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INTERNET-DRAFT                               Charles H. Lindsey
Usenet Format Working Group                  University of Manchester
                                             June 2003

                          News Article Format

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC 2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that
   other groups may also distribute working documents as Internet-

   Internet-Drafts are draft documents valid for a maximum of six
   months and may be updated, replaced, or obsoleted by other
   documents at any time. It is inappropriate to use Internet-Drafts
   as reference material or to cite them other than as "work in

   The list of current Internet-Drafts can be accessed at

   The list of Internet-Draft Shadow Directories can be accessed at


   This Draft is intended as a standards track document, obsoleting
   RFC 1036, which itself dates from 1987.

   This Standard defines the format of Netnews articles and specifies
   the requirements to be met by software which originates, distributes,
   stores and displays them.

   Since the 1980s, Usenet has grown explosively, and many Internet and
   non-Internet sites now participate. In addition, the Netnews
   technology is now in widespread use for other purposes.

   Backward compatibility has been a major goal of this endeavour, but
   where this standard and earlier documents or practices conflict, this
   standard should be followed. In most such cases, current practice is
   already compatible with these changes.

[Draft-10 removed all the Internationalization features (i.e. those
involving the use of the UTF-8 charset in headers). This is being done
so as to facilitate publishing those features, or similar ones, as an
experimental protocol at a later stage.

This present draft is derived from draft-10 by removing many
requirements which were present for Social rather than Normative reasons

C. H. Lindsey                                                   [Page 1]

                          News Article Format                  June 2003

(and in particular the word "Ought" with its specially defined meaning
is no longer used). These former requirements will now appear in a
companion Informational document/*(us.

There may well be a further split of the present draft into a
syntax/semantics part and a protocol part. Thus this present draft is
but an intermediate stage in an ongoing development process.]
[The use of the words "this standard" within this document when
referring to itself does not imply that this draft yet has pretensions
to be a standard, but rather indicates what will become the case if and
when it is accepted as an RFC with the status of a proposed or draft

[Remarks enclosed in square brackets and aligned with the left margin,
such as this one, are not part of this draft, but are editorial notes to
explain matters amongst ourselves, or to point out alternatives, or to
assist the RFC Editor.]

[In this draft, references to [NNTP] are to be replaced by [RFC 977], or
else by references to the RFC arising from the series of drafts draft-
ietf-nntpext-base-*.txt, in the event that such RFC has been accepted at
the time this document is published. Likewise, if may be possible to
replace references to [RFC 2279] by references to [RFC 2279bis].]

                           Table of Contents

1.  Introduction ..................................................    6
  1.1.  Basic Concepts ............................................    6
  1.2.  Objectives ................................................    6
  1.3.  Historical Outline ........................................    7
  1.4.  Transport .................................................    7
2.  Definitions, Notations and Conventions ........................    7
  2.1.  Definitions ...............................................    7
  2.2.  Textual Notations .........................................    9
  2.3.  Relation To Email and MIME ................................   10
  2.4.  Syntax ....................................................   10
    2.4.1.  Syntax Notation .......................................   10
    2.4.2.  Syntax adapted from Email and MIME ....................   11
    2.4.3.  Syntax copied from other standards ....................   13
  2.5.  Language ..................................................   15
3.  Changes to the existing protocols .............................   15
  3.1.  Principal Changes .........................................   15
  3.2.  Transitional Arrangements .................................   16
4.  Basic Format ..................................................   17
  4.1.  Syntax of News Articles ...................................   17
  4.2.  Headers ...................................................   18
    4.2.1.  Naming of Headers .....................................   18
    4.2.2.  MIME-style Parameters .................................   19
    4.2.3.  White Space and Continuations .........................   20
    4.2.4.  Comments ..............................................   21
    4.2.5.  Header Properties .....................................   22  Experimental Headers ..............................   22  Inheritable Headers ...............................   22

C. H. Lindsey                                                   [Page 2]

                          News Article Format                  June 2003  Variant Headers ...................................   22
    4.2.6.  Undesirable Headers ...................................   23
  4.3.  Body ......................................................   23
    4.3.1.  Body Format Issues ....................................   23
    4.3.2.  Body Conventions ......................................   23
  4.4.  Characters and Character Sets .............................   23
    4.4.1.  Character Sets within Article Headers .................   24
    4.4.2.  Character Sets within Article Bodies ..................   25
  4.5.  Size Limits ...............................................   25
  4.6.  Example ...................................................   26
5.  Mandatory Headers .............................................   26
  5.1.  Date ......................................................   26
    5.1.1.  Examples ..............................................   27
  5.2.  From ......................................................   27
    5.2.1.  Examples:  ............................................   27
  5.3.  Message-ID ................................................   28
  5.4.  Subject ...................................................   29
  5.5.  Newsgroups ................................................   29
    5.5.1.  Forbidden newsgroup-names .............................   31
  5.6.  Path ......................................................   31
    5.6.1.  Format ................................................   32
    5.6.2.  Adding a path-identity to the Path-header .............   32
    5.6.3.  The tail-entry ........................................   34
    5.6.4.  Path-Delimiter Summary ................................   34
    5.6.5.  Suggested Verification Methods ........................   35
    5.6.6.  Example ...............................................   35
6.  Optional Headers ..............................................   36
  6.1.  Reply-To ..................................................   36
    6.1.1.  Examples ..............................................   36
  6.2.  Sender ....................................................   36
  6.3.  Organization ..............................................   37
  6.4.  Keywords ..................................................   37
  6.5.  Summary ...................................................   37
  6.6.  Distribution ..............................................   37
  6.7.  Followup-To ...............................................   38
  6.8.  Mail-Copies-To ............................................   39
  6.9.  Posted-And-Mailed .........................................   39
  6.10.  References ...............................................   40
    6.10.1.  Examples .............................................   40
  6.11.  Expires ..................................................   41
  6.12.  Archive ..................................................   41
  6.13.  Control ..................................................   42
  6.14.  Approved .................................................   42
  6.15.  Supersedes ...............................................   43
  6.16.  Xref .....................................................   44
  6.17.  Lines ....................................................   44
  6.18.  User-Agent ...............................................   45
    6.18.1.  Examples .............................................   45
  6.19.  Injector-Info ............................................   46
    6.19.1.  Usage of Injector-Info-parameters ....................   47  The posting-host-parameter .......................   47  The posting-account-parameter ....................   48  The posting-sender-parameter .....................   48  The posting-logging-parameter ....................   48

C. H. Lindsey                                                   [Page 3]

                          News Article Format                  June 2003  The posting-date-parameter .......................   48
    6.19.2.  Example ..............................................   48
  6.20.  Complaints-To ............................................   48
  6.21.  MIME headers .............................................   49
    6.21.1.  Syntax ...............................................   49
    6.21.2.  Content-Type .........................................   50
    6.21.3.  Content-Transfer-Encoding ............................   50
    6.21.4.  Character Sets .......................................   51
    6.21.5.  Content Disposition ..................................   51
    6.21.6.  Definition of some new Content-Types .................   51  Application/news-transmission ....................   51  Message/news obsoleted ...........................   53
  6.22.  Obsolete Headers .........................................   53
7.  Control Messages ..............................................   53
  7.1.  Digital Signature of Headers ..............................   53
  7.2.  Group Control Messages ....................................   54
    7.2.1.  The 'newgroup' Control Message ........................   54  The Body of the 'newgroup' Control Message ........   55  Application/news-groupinfo ........................   55  Initial Articles ..................................   56  Example ...........................................   57
    7.2.2.  The 'rmgroup' Control Message .........................   58  Example ...........................................   58
    7.2.3.  The 'mvgroup' Control Message .........................   58  Example ...........................................   60
    7.2.4.  The 'checkgroups' Control Message .....................   60  Application/news-checkgroups ......................   61
  7.3.  Cancel ....................................................   62
  7.4.  Ihave, sendme .............................................   63
  7.5.  Obsolete control messages.  ...............................   64
8.  Duties of Various Agents ......................................   64
  8.1.  General principles to be followed .........................   64
  8.2.  Duties of an Injecting Agent ..............................   65
    8.2.1.  Proto-articles ........................................   65
    8.2.2.  Procedure to be followed by Injecting Agents ..........   65
  8.3.  Duties of a Relaying Agent ................................   67
  8.4.  Duties of a Serving Agent .................................   68
  8.5.  Duties of a Posting Agent .................................   69
  8.6.  Duties of a Followup Agent ................................   70
  8.7.  Duties of a Moderator .....................................   71
  8.8.  Duties of a Gateway .......................................   73
    8.8.1.  Duties of an Outgoing Gateway .........................   74
    8.8.2.  Duties of an Incoming Gateway .........................   74
    8.8.3.  Example ...............................................   76
9.  Security and Related Considerations ...........................   77
  9.1.  Leakage ...................................................   77
  9.2.  Attacks ...................................................   78
    9.2.1.  Denial of Service .....................................   78
    9.2.2.  Compromise of System Integrity ........................   79
  9.3.  Liability .................................................   80
10.  IANA Considerations ..........................................   81
11.  References ...................................................   81
12.  Acknowledgements .............................................   83
13.  Contact Address ..............................................   84

C. H. Lindsey                                                   [Page 4]

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Appendix A.1 - A-News Article Format ..............................   85
Appendix A.2 - Early B-News Article Format ........................   85
Appendix A.3 - Obsolete Headers ...................................   86
Appendix A.4 - Obsolete Control Messages ..........................   86
Appendix B - Collected Syntax .....................................   87
Appendix B.1 - Characters, Atoms and Folding ......................   87
Appendix B.2 - Basic Forms ........................................   89
Appendix B.3 - Headers ............................................   90
Appendix B.3.1 - Header outlines ..................................   90
Appendix B.3.2 - Control-message outlines .........................   92
Appendix B.3.3 - Other header rules ...............................   93
Appendix C - Notices ..............................................   95

C. H. Lindsey                                                   [Page 5]

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1.  Introduction

1.1.  Basic Concepts

   "Netnews" is a set of protocols for generating, storing and
   retrieving news "articles" (which resemble email messages) and for
   exchanging them amongst a readership which is potentially widely
   distributed. It is organized around "newsgroups", with the
   expectation that each reader will be able to see all articles posted
   to each newsgroup in which he participates. These protocols most
   commonly use a flooding algorithm which propagates copies throughout
   a network of participating servers.  Typically, only one copy is
   stored per server, and each server makes it available on demand to
   readers able to access that server.

   An important characteristic of Netnews is the lack of any requirement
   for a central administration or for the establishment of any
   controlling host to manage the network. A network which limits
   participation to some restricted set of hosts (within some company,
   for example) is a "closed" network; otherwise it is an "open"
   network. A set of hosts within a network which, by mutual
   arrangement, operates some variant (whether more or less restrictive)
   of the Netnews protocols is a "cooperating subnet".

   "Usenet" is a particular worldwide open network based upon the
   Netnews protocols, with the newsgroups being organized into
   recognized "hierarchies".  Anybody can join (it is simply necessary
   to negotiate an exchange of articles with one or more other
   participating hosts)

   A "policy" is a rule intended to facilitate the smooth operation of a
   network by establishing parameters which restrict behaviour that,
   whilst technically unexceptionable, would nevertheless contravene
   some accepted standard of "Good Netkeeping". Since the ultimate
   beneficiaries of a network are its human readers, who will be less
   tolerant of poorly designed interfaces than mere computers, articles
   in breach of established policy can cause considerable annoyance to
   their recipients.

1.2.  Objectives

   The purpose of this present standard is to define the format of
   articles and the protocols to be used for Netnews in general, and for
   Usenet in particular, and to set standards to be followed by software
   that implements those protocols.

   It is NOT the purpose of this standard to settle matters of policy,
   nor aspects of software behaviour which do not impinge upon the
   generation, transmission, storate and reception of articles, nor how
   the authority of various agencies to exercise control or oversight of
   the various parts of Usenet is established. For these purposes, a
   separate informational document [USEAGE] is being provided.

C. H. Lindsey                                                   [Page 6]

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   Nevertheless, it is assumed that agencies with the necessary
   authority will exist, and tools are provided within the protocols for
   their use.

1.3.  Historical Outline

   Network news originated as the medium of communication for Usenet,
   circa 1980.  Since then, Usenet has grown explosively, and many
   Internet and non-Internet sites participate in it.  In addition, the
   news technology is now in widespread use for other purposes, on the
   Internet and elsewhere.

   The earliest news interchange used the so-called "A News" article
   format.  Shortly thereafter, an article format vaguely resembling
   Internet Mail was devised and used briefly.  Both of those formats
   are completely obsolete; they are documented in Appendix A.1 and
   Appendix A.2 for historical reasons only.  With publication of [RFC
   850] in 1983, news articles came to closely resemble Internet Mail
   messages, with some restrictions and some additional headers. [RFC
   1036] in 1987 updated [RFC 850] without making major changes.

   A Draft popularly referred to as "Son of 1036" [Son-of-1036] was
   written in 1994 by Henry Spencer. That document formed the original
   basis for this standard, and its author has endorsed this standard as
   its successor.  Much is taken directly from Son of 1036, and it is
   hoped that we have followed its spirit and intentions. It is
   anticipated that [Son-of-1036] will be published as an Historic RFC,
   in a suitably relabelled form, following the publication of this

1.4.  Transport

   As in this standard's predecessors, the exact means used to transmit
   articles from one host to another is not specified. NNTP [NNTP] is
   the most common transmission method on the Internet, but much
   transmission takes place entirely independent of the Internet. Other
   methods in use include the UUCP protocol [RFC 976] extensively used
   in the early days of Usenet, FTP, downloading via satellite, tape
   archives, and physically delivered magnetic and optical media.

2.  Definitions, Notations and Conventions

2.1.  Definitions

   An "article" is the unit of news, analogous to an [RFC 2822]
   "message". A "proto-article" is one that has not yet been injected
   into the news system.

   A "message identifier" (5.3) is a unique identifier for an article,
   usually supplied by the "posting agent" which posted it or, failing
   that, by the "injecting agent". It distinguishes the article from
   every other article ever posted anywhere. Articles with the same
   message identifier are treated as if they are the same article
   regardless of any differences in the body or headers.

C. H. Lindsey                                                   [Page 7]

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   A "newsgroup" is a single news forum, a logical bulletin board,
   having a name and nominally intended for articles on a specific
   topic. An article is "posted to" a single newsgroup or several
   newsgroups. When an article is posted to more than one newsgroup, it
   is said to be "crossposted"; note that this differs from posting the
   same text as part of each of several articles, one per newsgroup.

   A newsgroup may be "moderated", in which case submissions are not
   posted directly, but mailed to a "moderator" for consideration and
   possible posting.  Moderators are typically human but may be
   implemented partially or entirely in software.

   A "hierarchy" is the set of all newsgroups whose names share a first
   component (as defined in 5.5).  The term "sub-hierarchy" is also used
   where several initial components are shared.

   A "poster" is the person or software that composes and submits a
   possibly compliant article to a "posting agent". The poster is
   analogous to [RFC 2822]'s author(s).

   A "posting agent" is the software that assists posters to prepare
   proto-articles, in compliance with this standard. The proto-article
   is then passed on to an "injecting agent" for final checking and
   injection into the news stream. If the article is not compliant, or
   is rejected by the injecting agent, then the posting agent informs
   the poster with an explanation of the error.

   A "reader" is the person or software reading news articles.

   A "reading agent" is software which presents articles to a reader.

   A "followup" is an article containing a response to the contents of
   an earlier article (the followup's "precursor").

   A "followup agent" is a combination of reading agent and posting
   agent that aids in the preparation and posting of a followup.

   An (email) "address" is the mailbox [RFC 2822] (or more particularly
   the addr-spec within that mailbox) which directs the delivery of an
   email to its intended recipient, who is said to "own" that address.

   An article's "reply address" is the address to which mailed replies
   should be sent. This is the address specified in the article's From-
   header (5.2), unless it also has a Reply-To-header (6.1).

   A "sender" is the person or software (usually, but not always, the
   same as the poster) responsible for the operation of the posting
   agent or, which amounts to the same thing, for passing the article to
   the injecting agent. The sender is analogous to [RFC 2822]'s sender.

   An "injecting agent" takes the finished article from the posting
   agent (often via the NNTP "post" command) performs some final checks
   and passes it on to a relaying agent for general distribution.

C. H. Lindsey                                                   [Page 8]

                          News Article Format                  June 2003

   A "relaying agent" is software which receives allegedly compliant
   articles from injecting agents and/or other relaying agents, and
   possibly passes copies on to other relaying agents and serving

   A "news database" is the set of articles and related structural
   information stored by a serving agent and made available for access
   by reading agents.

   A "serving agent" receives an article from a relaying agent and files
   it in a news database. It also provides an interface for reading
   agents to access the news database.

   A "control message" is an article which is marked as containing
   control information; a relaying or serving agent receiving such an
   article may (subject to the policies observed at that site) take
   actions beyond just filing and passing on the article.

   A "gateway" is software which receives news articles and converts
   them to messages of some other kind (e.g. mail to a mailing list), or
   vice versa; in essence it is a translating relaying agent that
   straddles boundaries between different methods of message exchange.
   The most common type of gateway connects newsgroup(s) to mailing
   list(s), either unidirectionally or bidirectionally, but there are
   also gateways between news networks using this standard's news format
   and those using other formats.

2.2.  Textual Notations

   This standard contains explanatory NOTEs using the following format.
   These may be skipped by persons interested solely in the content of
   the specification. The purpose of the notes is to explain why choices
   were made, to place them in context, or to suggest possible
   implementation techniques.

        NOTE: While such explanatory notes may seem superfluous in
        principle, they often help the less-than-omniscient reader grasp
        the purpose of the specification and the constraints involved.
        Given the limitations of natural language for descriptive
        purposes, this improves the probability that implementors and
        users will understand the true intent of the specification in
        cases where the wording is not entirely clear.

   "US-ASCII" is short for "the ANSI X3.4 character set" [ANSI X3.4].
   While "ASCII" is often misused to refer to various character sets
   somewhat similar to X3.4, in this standard "US-ASCII" is used to mean
   X3.4 and only X3.4. US-ASCII is a 7 bit character set. Please note
   that this standard requires that all agents be 8 bit clean; that is,
   they must accept and transmit data without changing or omitting the
   8th bit.

   Certain words, when capitalized, are used to define the significance
   of individual requirements. The key words "MUST", "REQUIRED",
   "SHOULD", "RECOMMENDED", "MAY" and "OPTIONAL", and any of those words

C. H. Lindsey                                                   [Page 9]

                          News Article Format                  June 2003

   associated with the word "NOT", are to be interpreted as described in
   [RFC 2119].

        NOTE: The use of "MUST" or "SHOULD" implies a requirement that
        would or could lead to interoperability problems if not

        NOTE: A requirement imposed on a relaying or serving agent
        regarding some particular article should be understood as
        applying only if that article is actually accepted for
        processing (since any agent may always reject any article
        entirely, for reasons of site policy).

   Wherever the context permits, use of the masculine includes the
   feminine and use of the singular includes the plural, and vice versa.

   Throughout this standard we will give examples of various
   definitions, headers and other specifications. It needs to be
   remembered that these samples are for the aid of the reader only and
   do NOT define any specification themselves.  In order to prevent
   possible conflict with "Real World" entities and people the top level
   domain ".example" is used in all sample domains and addresses. The
   hierarchy "example.*" is also used as a sample hierarchy.
   Information on the ".example" top level domain is in [RFC 2606].

2.3.  Relation To Email and MIME

   The primary intent of this standard is to describe the news article
   format.  Insofar as news articles are a subset of the email message
   format augmented by some new headers, this standard incorporates many
   (though not all) of the provisions of [RFC 2822], with the aim of
   enabling news articles to pass through email systems and vice versa,
   provided only that they contain the minimum headers required for the
   mode of transport being used. Unfortunately, the match is not
   perfect, but it is the intention of this standard that gateways
   between Email and Netnews should be able to operate with the minimum
   of tinkering.

   Likewise, this standard incorporates (see section 6.21) many, though
   not all, of the provisions of the MIME standards [RFC 2045] et seq
   which, though designed with Email in mind, are mostly applicable to

2.4.  Syntax

   The complete syntax defined in this standard is repeated, for
   convenience, in Appendix B.

2.4.1.  Syntax Notation

   This standard uses the Augmented Backus Naur Form described in [RFC

C. H. Lindsey                                                  [Page 10]

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   In particular, it makes significant use of the "incremental
   alternative" feature of that notation. For example, the two rules
      header              = other-header
      header              =/ Date-header
   are equivalent to the single rule
      header              = other-header / Date-header

2.4.2.  Syntax adapted from Email and MIME

   Much of the syntax of Netnews Articles is based on the corresponding
   syntax defined in [RFC 2822].  Therefore, wherever in this standard
   the syntax is stated to be taken from [RFC 2822], it is to be
   understood, unless explicitly stated to the contrary, as the syntax
   defined by [RFC 2822], but NOT including any syntax defined in
   section 4 ("Obsolete syntax") of [RFC 2822].  Software compliant with
   this standard MUST NOT generate any of the syntactic forms defined in
   that Obsolete Syntax, although it MAY accept such syntactic forms.

   Likewise, certain syntax from the MIME specifications [RFC 2045] et
   seq is also considered to have been incorporated into this standard
   (see 6.21).

   However, there are some differences arising from some special
   requirements of Netnews, and the following syntactic rules therefore
   supersede the corresponding rules given in [RFC 2822].

        NOTE: Netnews parsers historically have been much less
        permissive than Email parsers, and this is reflected in the
        modifications referred to, and in some further specific rules.

   In contradistinction to [RFC 2822], an unstructured header (e.g. a
   Subject-header) MUST contain at least one non-whitespace character
   (see also remarks about empty headers in 4.2.6).

      unstructured    = 1*( [FWS] ( utext / encoded-word ) ) [FWS]

   Extended-phrases (known somewhat confusingly in [RFC 2822] as obs-
   phrases) are introduced to allow headers such as
      From: Joe Q. Public <joe@public.example>
   without the necessity of using a quoted-string. They MUST be accepted
   by compliant software, but they SHOULD NOT be generated until
   software capable of accepting them has become widely deployed.

      phrase          = 1*( [CFWS] encoded-word [CFWS] / word ) /
      extended-phrase = ( [CFWS] encoded-word [CFWS] / word )
                           *( [CFWS] encoded-word [CFWS] / word  /
                              [CFWS] "." [CFWS] )
[ [RFC 2822] had
      obs-phrase      = word *( word / "." / CFWS )
Please can Pete check that what I have is equivalent?]

C. H. Lindsey                                                  [Page 11]

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   Within a date-time, two of the obs-zones from [RFC 2822] are retained
   because of current widespread usage.

      zone            = (( "+" / "-" ) 4DIGIT) / "UT" / "GMT"

   The forms "UT" and "GMT" (indicating universal time) are to be
   regarded as obsolete synonyms for "+0000". They MUST be accepted, and
   passed on unchanged, by all agents, but they MUST NOT be generated as
   part of new articles by posting and injecting agents.

   Msg-ids are redefined to be a "normalized" subset of those defined by
   [RFC 2822], ensuring that no string of characters is quoted unless
   strictly necessary (it must contain at least one mqspecial) and no
   single character is prefixed by a "\" in the form of a quoted-pair
   unless strictly necessary, and moreover there is no possibility for
   ">" or WSP to occur inside a msg-id, whether quoted or not. Thus,
   whereas under [RFC 2822]
   would be considered semantically equivalent, only the first of them
   is syntactically permitted by this standard, and hence a simple
   comparison of octets will always suffice to determine the identity of
   two msg-ids.

      msg-id          = "<" id-left "@" id-right ">"
      id-left         = dot-atom-text / no-fold-quote
      id-right        = dot-atom-text / no-fold-literal
      no-fold-quote   = DQUOTE
                           *( mqtext / "\\" / "\" DQUOTE )
                           *( mqtext / "\\" / "\" DQUOTE )
      mqtext          = NO-WS-CTL /      ; all of <text> except
                        %d33 /           ; SP, HTAB, "\", ">"
                        %d35-61 /        ; and DQUOTE
                        %d63-91 /
      mqspecial       = "(" / ")" /      ; same as specials except
                        "<" /            ; "\" and DQUOTE quoted
                        "[" / "]" /      ; and ">" omitted
                        ":" / ";" /
                        "@" / "\\" /
                        "," / "." /
                        "\" DQUOTE
      no-fold-literal = "[" *( mdtext / "\[" / "\]" / "\\" ) "]"
      mdtext          = NO-WS-CTL /      ; Non white space controls
                        %d33-61 /        ; The rest of the US-ASCII
                        %d63-90 /        ; characters not including
                        %d94-126         ; ">", "[", "]", or "\"

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2.4.3.  Syntax copied from other standards

   The following syntactic forms, taken from [RFC 2234] or from [RFC
   2822] and adapted to incorporate variations introduced in [RFC 2047],
   are repeated here for convenience only:

      ALPHA         = %x41-5A /          ; A-Z
                      %x61-7A            ; a-z
      CR            = %x0D               ; carriage return
      CRLF          = CR LF
      DIGIT         = %x30-39            ; 0-9
      HTAB          = %x09               ; horizontal tab
      LF            = %x0A               ; line feed
      SP            = %x20               ; space
      NO-WS-CTL     = %d1-8 /            ; US-ASCII control characters
                      %d11 /             ; which do not include the
                      %d12 /             ; carriage return, line feed,
                      %d14-31 /          ; and whitespace characters
      specials      = "(" / ")" /        ; Special characters used in
                      "<" / ">" /        ; other parts of the syntax
                      "[" / "]" /
                      ":" / ";" /
                      "@" / "\" /
                      "," / "." /
      WSP           = SP / HTAB          ; whitespace characters
      FWS           = ([*WSP CRLF] 1*WSP); folding whitespace
      ccontent      = ctext / quoted-pair / comment / encoded-word
      comment       = "(" *([FWS] ccontent) [FWS] ")"
      CFWS          = *([FWS] comment) ( ([FWS] comment) / FWS )
      DQUOTE        = %d34               ; quote mark
      quoted-pair   = "\" text
      atext         = ALPHA / DIGIT /
                      "!" / "#" /        ; Any US-ASCII character except
                      "$" / "%" /        ; controls, SP, and specials.
                      "&" / "'" /        ; Used for atoms
                      "*" / "+" /
                      "-" / "/" /
                      "=" / "?" /
                      "^" / "_" /
                      "`" / "{" /
                      "|" / "}" /
      atom          = [CFWS] 1*atext [CFWS]
      dot-atom      = [CFWS] dot-atom-text [CFWS]
      dot-atom-text = 1*atext *( "." 1*atext )
      qcontent      = qtext / quoted-pair
      quoted-string = [CFWS] DQUOTE
                         *( [FWS] qcontent ) [FWS]
                         DQUOTE [CFWS]
      word          = atom / quoted-string

   The following are taken from [RFC 2045] and [RFC 2231] adapted to use

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   the folding syntax from [RFC 2822]:

      charset       = <registered character set name>
                                         ;  [RFC 2978]
      language      = <registered language tag>
                                         ;  [RFC 3066]
      encoded-word  = "=?" charset ["*" language] "?" encoding
                         "?" encoded-text "?="
      parameter     = regular-parameter / extended-parameter
      regular-parameter       = [CFWS] regular-parameter-name [CFWS]
                         "=" value
      regular-parameter-name  = attribute [section]
      attribute     = 1*attribute-char
      attribute-char= <any (US-ASCII) CHAR except SPACE, CTLs,
                         "*", "'", "%", or tspecials>
      tspecials     = "(" / ")" / "<" / ">" / "@" /
                      "," / ";" / ":" / "\" / DQUOTE /
                      "/" / "[" / "]" / "?" / "="
                    = ( [CFWS] extended-initial-name [CFWS]
                         "=" extended-initial-value ) /
                      ( [CFWS] extended-other-names [CFWS]
                         "=" extended-other-values )
      value         = [CFWS] token [CFWS] / quoted-string
      token         = 1*<any (US-ASCII) CHAR except SP, CTLs,
                         or tspecials>

        NOTE: Following [RFC 2234], literal text included in the syntax
        is to be regarded as case-insensitive.  However, in
        contradistinction to [RFC 2822], the Netnews protocols are
        sensitive to case in some instances (as in newsgroup-names, some
        header parameters, etc.). Care has been taken to indicate this
        explicitly where required.

   As in [RFC 2822], where any quoted-pair appears it is to be
   interpreted as its text character alone. That is to say, the "\"
   character that appears as part of a quoted-pair is semantically

   Again, as in [RFC 2822], strings of characters that include
   characters not syntactically allowed in some particular context may
   be incorporated into a quoted-string by "encapsulating" them between
   quote (DQUOTE, US-ASCII 34) characters, prefixing every quote and
   backslash character (and possibly other characters too) with a "\" so
   as to form a quoted-pair, and possibly introducing folding by
   prefixing some WSP with CRLF.

   The semantic value of a quoted-string (i.e. the result of reversing
   the encapsulation) is a string of characters which includes neither
   the optional CFWS outside of the quote characters, nor the quote
   characters themselves, nor any CRLF contained within any FWS between
   the two quote characters, nor the "\" which introduces any quoted-

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   For the purposes of section 5 of [RFC 2047] all headers (4.1) defined
   in this standard are to be considered as "extension message header
   fields" (insofar as they are not already so considered under the
   existing Email standards), permitting the use of [RFC 2047] encodings
   within any unstructured header, or within any comment or phrase
   permitted within any structured header.

   The syntax of encoded-text and of encoding can be found in [RFC
   2047], and there are restrictions on the characters that may occur
   within an encoded-text, depending on its context. There are also
   restrictions on the overall length of an encoded-word and of headers
   containing encoded-words and requirements for encoded-words to have
   FWS on either side of them in most contexts. All these restrictions
   and requirements MUST be observed.

2.5.  Language

   Various constant strings in this standard, such as header-names and
   month names, are derived from English words. Despite their
   derivation, these words do NOT change when the poster or reader
   employing them is interacting in a language other than English.
   Posting and reading agents MAY translate as appropriate in their
   interaction with the poster or reader, but the forms that actually
   appear in articles as transmitted MUST be the English-derived ones
   defined in this standard.

3.  Changes to the existing protocols

   This standard prescribes many changes, clarifications and new
   features since the protocols described in [RFC 1036] and [Son-of-
   1036].  It is the intention that they can be assimilated into Usenet
   as it presently operates without major interruption to the service,
   though some of the new features may not begin to show benefit until
   they become widely implemented. This section summarizes the main
   changes, and comments on some features of the transition.

3.1.  Principal Changes

     o The [RFC 2822] conventions for parenthesis-enclosed comments in
       headers are supported.
     o Whitespace is permitted in Newsgroups-headers, permitting folding
       of such headers. Indeed, all headers can now be folded.
     o An enhanced syntax for the Path-header enables the injection
       point of and the route taken by an article to be determined with
     o Large parts of MIME are recognized as an integral part of
     o There is a new Control message 'mvgroup' to facilitate moving a
       group to a different place (name) in a hierarchy.
     o There are several new headers defined, notably Archive,
       Complaints-To, Injector-Info, Mail-Copies-To, Posted-And-Mailed
       and User-Agent, leading to increased functionality.
     o Provision has been made for almost all headers to have MIME-style
       parameters (to be ignored if not recognized), thus facilitating

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       extension of those headers in future standards.
     o Certain headers and Control messages (Appendix A.3 and Appendix
       A.4) have been made obsolete.
     o Distributions are expected to be checked at the receiving end, as
       well as the sending end, of a relaying link.
     o There are numerous other small changes, clarifications and

3.2.  Transitional Arrangements

   An important distinction must be made between serving and relaying
   agents, which are responsible for the distribution and storage of
   news articles, and user agents, which are responsible for
   interactions with users. It is important that the former should be
   upgraded to conform to this standard as soon as possible to provide
   the benefit of the enhanced facilities.  Fortunately, the number of
   distinct implementations of such agents is rather small, at least so
   far as the main "backbone" of Usenet is concerned, and many of the
   new features are already supported. Contrariwise, there are a great
   number of implementations of user agents, installed on a vastly
   greater number of small sites. Therefore, the new functionality has
   been designed so that existing agents may continue to be used,
   although the full benefits may not be realised until a substantial
   proportion of them have been upgraded.

   In the list which follows, care has been taken to distinguish the
   implications for both kinds of agent.

     o [RFC 2822] style comments in headers do not affect serving and
       relaying agents (note that the Message-ID-, Newsgroups-,
       Distribution- and Path-headers do not contain them). They are
       unlikely to hinder their proper display in existing reading
       agents except in the case of the References-header in agents
       which thread articles. Therefore, it is provided that they SHOULD
       NOT be generated except where permitted by the previous
     o Because of its importance to all serving agents, the extension
       permitting whitespace and folding in Newsgroups-headers SHOULD
       NOT be used until it has been widely deployed amongst relaying
       agents. User agents are unaffected.
     o The new style of Path-header is already consistent with the
       previous standards. However, the intention is that relaying
       agents should eventually reject articles in the old style, and so
       this possibility should be offered as a configurable option in
       relaying agents. User agents are unaffected.
     o The introduction of MIME reflects a practice that is already
       widespread.  Articles in strict compliance with the previous
       standards (using strict US-ASCII) will be unaffected. Many user
       agents already support it, at least to the extent of widely used
       charsets such as ISO-8859-1. Users expecting to read articles
       using other charsets will need to acquire suitable reading
       agents. It is not intended, in general, that any single user
       agent will be able to display every charset known to IANA, but
       all such agents MUST support US-ASCII. Serving and relaying

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       agents are not affected.
     o The new Control: mvgroup command will need to be implemented in
       serving agents. For the benefit of older serving agents it is
       therefore RECOMMENDED that it be followed shortly by a
       corresponding newgroup command and it MUST always be followed by
       a rmgroup command for the old group after a reasonable overlap
       period. An implementation of the mvgroup command as an alias for
       the newgroup command would thus be minimally conforming. User
       agents are unaffected.
     o All the headers newly introduced by this standard can safely be
       ignored by existing software, albeit with loss of the new

4.  Basic Format

4.1.  Syntax of News Articles

   The overall syntax of a news article is:

      article           = 1*( header CRLF ) separator body
      header            = other-header
      other-header      = header-name ":" 1*SP other-content
      header-name       = 1*name-character *( "-" 1*name-character )
      name-character    = ALPHA / DIGIT
      other-content     = <the content of a header defined by some
                           other standard>
      separator         = CRLF
      body              = *( *998text CRLF )

   However, the rule given above for header is incomplete. Further
   alternatives will be added incrementally as the various Netnews
   headers are introduced in this standard (or in future extensions),
   using the "=/" notation defined in [RFC 2234].  For example, a
   typical Usenet-header would be defined as follows:

      header            =/ Usenet-header
      Usenet-header     = "Usenet" ":" SP Usenet-content
                             *( ";" ( Usenet-parameter /
                                      extension-parameter ) )
      Usenet-content    = <syntax specific to that Usenet-header>
      Usenet-parameter  = <a parameter specific to that Usenet-header>

   where the Usenet-parameter, which MUST always be of the same
   syntactic form as a parameter, is not provided in all headers, and
   even the extension-parameter is omitted in some cases (see 4.2.2).
   Observe that "Usenet" is (and MUST be) of the syntactic form of a

                        = <a parameter not defined by this standard>
      x-attribute     = "x-" attribute

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   An article consists of some headers followed by a body. An empty line
   separates the two. The headers contain structured information about
   the article and its transmission. A header begins with a header-name
   identifying it, and can be continued onto subsequent lines as
   described in section 4.2.3.  The body is largely unstructured text
   significant only to the poster and the readers.

        NOTE: Terminology here follows the current custom in the news
        community, rather than the [RFC 2822] convention of referring to
        what is here called a "header" as a "header-field" or "field".

   Note that the separator line MUST be truly empty, not just a line
   containing white space. Further empty lines following it are part of
   the body, as are empty lines at the end of the article.

        NOTE: The syntax above defines the canonical form of a news
        article as a sequence of lines each terminated by CRLF. This
        does not prevent serving agents or transport agents from storing
        or handling the article in other formats (e.g. using a single LF
        in place of CRLF) so long as the overall effects achieved are as
        defined by this standard when operating on the canonical form.

4.2.  Headers

   The order of headers in an article is not significant. However,
   posting agents are encouraged to put mandatory headers (section 5)
   first, followed by optional headers (section 6), followed by
   experimental headers and headers not defined in this standard or its
   extensions. Relaying agents MUST NOT change the order of the headers
   in an article.

4.2.1.  Naming of Headers

   Despite the restrictions on header-name syntax imposed by the
   grammar, relaying, serving and reading agents SHOULD tolerate
   header-names containing any US-ASCII printable character other than
   colon (":", US-ASCII 58).

   Whilst relaying agents MUST accept, and pass on unaltered, any non-
   variant header whose header-name is syntactically correct, and
   reading agents MUST enable them to be displayed, at least optionally,
   posting and injecting agents SHOULD NOT generate headers other than
     o headers established by this standard or any extension to it;
     o those recognized by other IETF-established standards, notably the
       Email standard [RFC 2822] and its extensions, excluding any
       explicitly deprecated for Netnews (e.g. see section 9.2.1 for the
       deprecated Disposition-Notification-To-header); or,
       alternatively, those listed in some future IANA registry of
       recognized headers;
     o experimental headers beginning with "X-" (as defined in;
     o on a provisional basis only, headers related to new protocols
       under development which are the subject of (or intended to be the
       subject of) some IETF-approved RFC (whether Informational,
       Experimental or Standards-Track).

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   However, software SHOULD NOT attempt to interpret headers not
   specifically intended to be meaningful in the Netnews environment.
[However, if [KLYNE], which defines an IANA registry of recognized
headers, becomes accepted before we are done (which is likely), then
that paragraph can be simplified very considerably.]

   Header-names are case-insensitive. There is a preferred case
   convention set out in [USEAGE], and which is used in the various
   rules defining headers in this standard.  Relaying and reading agents
   MUST, however, tolerate header-names in any case.

4.2.2.  MIME-style Parameters

   A few header-specific MIME-style parameters are defined in this
   standard, but there is also provision for generic extension-
   parameters to appear in most headers for the purpose of allowing
   future extensions to those headers. Observe that such parameters do
   not, in general, occur in headers defined in other standards, except
   for the MIME standards [RFC 2045] et seq. and their extensions.

   Extension-parameters, other than those using x-attributes, MUST NOT
   be used unless they have first been defined in an IETF-approved RFC
   (whether Informational, Experimental or Standards-Track) or, on a
   provisional basis only, in relation to new protocols under
   development which are the subject of (or intended to be the subject
   of) some such IETF-approved RFC. They MUST ONLY be defined for use in
   those headers where the syntax of this standard so allows. They
   SHOULD NOT, at present, be defined for use in headers in widespread
   use prior to the introduction of this standard (this restriction is
   likely to be removed in a future version of this standard).
   Nevertheless, compliant software MUST accept such parameters wherever
   syntactically allowed in this standard (ignoring them if their
   meaning is unknown) and SHOULD accept (and ignore) them in all
   structured headers wherever defined.
[We could go further, and establish an IANA registry for these
parameters, preloaded with the ones already defined in this standard. A
good model for setting up such a registry is to be found in RFC 2183

        NOTE: The syntax does not permit extension-parameters in
        unstructured headers (where they are unnecessary) or in certain
        headers (notably the Date-, From-, Message-ID-, Reply-To-,
        Sender-, Keywords-, Mail-Copies-To-, References-, Supersedes-
        and Complaints-To-headers) which are the same (or similar to)
        headers already existing in the Email standards.

   Each header-specific MIME-style parameter introduced in this standard
   is described by specifying
     (a) its attribute, and
     (b) the syntax rule(s) defining the object(s) permitted in its
   Any parameter, or set of parameters with numbered sections, which,
   according to [RFC 2231], is semantically equivalent to an unnumbered
   regular-parameter with that attribute and value may be used.

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        NOTE: If the value is not of the syntactic form of a token and
        is not encoded as an extended-value, it is necessary to
        encapsulate it within a quoted-string (see 2.4.3).  Observe that
        the syntax of a parameter also allows additional WSP, folding
        and comments.

   The semantics of a parameter is always to associate its attribute
   with the object represented by the token, or the semantic value
   (2.4.3) of the quoted-string, contained in its value.

   For example, the posting-sender-parameter (6.19) is defined to be
      <a parameter with attribute "sender" and value some sender-value>
      sender-value      = mailbox / "verified"
   A valid posting-sender-parameter would be
      sender = "\"Joe D. Bloggs\" <jdbloggs@bloggs.example>" (authinfo)
   The comment (syntactically part of the quoted-string) is irrelevant.
   The actual mailbox (to be used, for example, if email is to be sent
   to the sender) is
      "Joe D. Bloggs" <jdbloggs@bloggs.example>

4.2.3.  White Space and Continuations

   Each header is logically a single line of characters comprising the
   header-name, the colon with its following SP, the content, and any
   parameters. For convenience, however, the content and parameters can
   be "folded" into a multiple line representation by inserting a CRLF
   before any WSP contained within any FWS or CFWS (but not any other SP
   or HTAB) allowed by this standard. For example, the header:
      Approved: modname@modsite.example (Moderator of example.foo.bar)
   can be represented as:
      Approved: modname@modsite.example
       (Moderator of example.foo.bar)

   FWS occurs at many places in the syntax (usually within a CFWS) in
   order to allow the inclusion of comments, whitespace and folding. The
   syntax is in fact ambiguous insofar as it sometimes allows two
   consecutive instantiations of FWS (as least one of which is always
   optional), or of an optional FWS followed by an explicit CRLF.
   However, all such cases MUST be treated as if the optional
   instantiation (or one of them) had not been allowed. It is thus
   precluded that any line of a header should be made up of whitespace
   characters and nothing else (for such a line might otherwise have
   been interpreted by a non-compliant agent as the separator between
   the headers and the body of the article).

        NOTE: This does not lead to semantic ambiguity because, unless
        specifically stated otherwise, the presence or absence of
        folding, a comment or additional WSP has no semantic meaning
        and, in particular, it is a matter of indifference whether it
        forms a part of the syntactic construct preceding it or the one
        following it.

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        NOTE: It may be observed that the content part of every header
        begins and ends with an optional CFWS (or FWS in the case of a
        few headers). Moreover, every parameter also begins and ends
        with an optional CFWS.

   In accordance with the syntax, the header-name on the first line MUST
   be followed by a SP (even if the rest of the header is empty, but see
   4.2.6).  Even though the syntax allows otherwise, at least some of
   the content MUST appear on that first line (to avoid the possibility
   of harm by any non-compliant agent that might eliminate a trailing
   WSP). Although posting agents are REQUIRED to enforce these
   restrictions, relaying and serving agents SHOULD accept articles that
   violate them.

        NOTE: This standard differs from [RFC 2822] in requiring that SP
        following the colon (it was also an [RFC 1036] requirement).

   Posters and posting agents SHOULD use SP, not HTAB, where white space
   is desired in headers (some existing software expects this). Relaying
   and serving agents SHOULD accept HTAB in all such cases, however.

   Relaying and serving agents MUST NOT refold headers (i.e. they must
   pass on the folding as received).


   Strings of characters which are treated as comments may be included
   in headers wherever the syntactic element CFWS occurs.  They consist
   of characters enclosed in parentheses.  Comments may be nested.

        NOTE: Although CFWS occurs wherever whitespace is allowed in
        almost all headers, there are exceptions where only FWS is
        permitted (hence folding but no comments). Notably, this happens
        in the case of the Message-ID-, Newsgroups-, Distribution-,
        Path- and Followup-To-headers, and within the Date-header except
        right at the end.

   Since a comment is allowed to contain FWS, folding is permitted
   within it as well as immediately preceding and immediately following
   it. Also note that, since quoted-pair is allowed in a comment, the
   parenthesis and backslash characters may appear in a comment so long
   as they appear as a quoted-pair. Semantically, the enclosing
   parentheses are not part of the content of the comment; the content
   is what is contained between the two parentheses.

   Since comments have not hitherto been permitted in news articles,
   except in a few specified places, posters and posting-agents SHOULD
   NOT insert them except in those places, namely following mailboxes in
   From and similar headers (a now deprecated convention for indicating
   the owner of that mailbox), and to indicate the name of the timezone
   in Date-headers. However, compliant software MUST accept them in all
   places where they are syntactically allowed.

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4.2.5.  Header Properties

   There are three special properties that may apply to particular
   headers, namely: "experimental", "inheritable", and "variant". When a
   header is defined, in this (or any future) standard, as having one
   (or possibly more) of these properties, it is subject to special
   treatment, as indicated below.  Experimental Headers

   Experimental headers are those whose header-names begin with "X-".
   They are to be used for experimental Netnews features, or for
   enabling additional material to be propagated with an article. They
   are not (and will not be) defined by this, or any, standard.

        NOTE: Experimental headers are suitable for situations where
        they need only to be human readable. They are not intended to be
        recognized by widely deployed Netnews software and, should such
        a requirement be envisaged, it is preferable to use a normal
        header on the provisional basis set out in section 4.2.1.  Inheritable Headers

   Subject only to the overriding ability of the poster to determine the
   contents of the headers in a proto-article, headers with the
   inheritable property MUST be copied by followup agents (perhaps with
   some modification) into the followup article, and headers without
   that property MUST NOT be so copied.  Examples include:
     o Newsgroups (5.5) - copied from the precursor, subject to any
     o Subject (5.4) - modified by prefixing with "Re: ", but otherwise
       copied from the precursor.
     o References (6.10) - copied from the precursor, with the addition
       of the precursor's Message-ID.
     o Distribution (6.6) - copied from the precursor.

        NOTE: The Keywords-header is not inheritable, though some older
        newsreaders treated it as such.  Variant Headers

   Headers with the variant property may differ between (or even be
   completely absent from) copies of the same article as stored or
   relayed throughout a Netnews system. The manner of the difference (or
   absence) MUST be as specified in this (or any future) standard.
   Typically, these headers are modified as articles are propagated, or
   they reflect the status of the article on a particular serving agent,
   or cooperating group of such agents. The variant header MAY be placed
   anywhere within the headers (though placing it first is recommended).
   The principal examples are:
     o Path (5.6) - augmented at each relaying agent that an article
       passes through.
     o Xref (6.16) - used to keep track of the article locators of
       crossposted articles so that newsreaders serviced by a particular

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       serving agent can mark such articles as read.

4.2.6.  Undesirable Headers

   A header whose content is empty is said to be an empty header (in
   fact, no such headers are defined by this standard).  Relaying and
   reading agents SHOULD NOT consider presence or absence of an empty
   header to alter the semantics of an article (although syntactic
   rules, such as requirements that certain header-names appear at most
   once, MUST still be satisfied). Posting and injecting agents SHOULD
   delete empty headers from articles before posting them; relaying
   agents MUST pass them untouched.

4.3.  Body

4.3.1.  Body Format Issues

   The body of an article SHOULD NOT be empty. A posting or injecting
   agent which does not reject such an article entirely SHOULD at least
   issue a warning message to the poster and supply a non-empty body.
   Note that the separator line MUST be present even if the body is

        NOTE: Some existing news software is known to react badly to
        body-less articles, hence the request for posting and injecting
        agents to insert a body in such cases. The sentence "This
        article was probably generated by a buggy news reader" has
        traditionally been used in this situation.

   Note that an article body is a sequence of lines terminated by CRLFs,
   not arbitrary binary data, and in particular it MUST end with a CRLF.
   However, relaying and serving agents SHOULD treat the body of an
   article as an uninterpreted sequence of octets (except as mandated by
   changes of CRLF representation and by control message processing, as
   in 7.2.4) and SHOULD avoid imposing constraints on it. See also
   section 4.5.

4.3.2.  Body Conventions

   A body is by default an uninterpreted sequence of octets for most of
   the purposes of this standard. However, a MIME Content-Type-header
   may impose some structure or intended interpretation upon it, and may
   also specify the character set in accordance with which the octets
   are to be interpreted.

4.4.  Characters and Character Sets

   Transmission paths for news articles MUST treat news articles as
   uninterpreted sequences of octets, excluding the values 0 (US-ASCII
   NUL) and 13 and 10 (US-ASCII CR and LF, which MUST ONLY appear in the
   combination CRLF which denotes a line separator).

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        NOTE: this corresponds to the range of octets permitted for MIME
        "8bit data" [RFC 2045].  Thus raw binary data cannot be
        transmitted in an article body except by the use of a Content-
        Transfer-Encoding such as base64.

   In particular, transmission paths MUST convey all headers (including
   body part headers and headers within message/rfc822 objects) intact,
   even if they contain octets representing non-ASCII charsets.  These
   requirements include the transmissiom paths between posting agents,
   injecting agents, relaying agents, serving agents and reading agents,
   but NOT the paths traversed by Netnews articles that have been
   gatewayed into Email (8.8.1).
[At some point it will be necessary for the IMAP standards to catch up
with these requirements.]

   Character data is represented by octets in accordance with some
   encoding scheme (US-ASCII for headers, and determined by the
   Content-Type- and Content-Transfer-Encoding-headers for bodies).

   If it comes to a relaying agent's attention that it is being asked to
   pass an article using the Content-Transfer-Encoding "8bit" to a
   relaying agent that does not support it, it SHOULD report this error
   to its administrator. It MUST refuse to pass the article and MUST NOT
   re-encode it with different MIME encodings.

        NOTE: This strategy will do little harm. The target relaying
        agent is unlikely to be able to make use of the article on its
        own servers, and the usual flooding algorithm will likely find
        some alternative route to get the article to destinations where
        it is needed.

4.4.1.  Character Sets within Article Headers

   Where the use of non-ASCII characters is required, they MUST be
   encoded using the MIME mechanisms defined in [RFC 2047] and [RFC

      Organization: Technische =?iso-8859-1?Q?Universit=E4t_M=FCnchen?=
      Approved: =?iso-8859-1?Q?Fran=E7ois_Faur=E9?= <ff@modsite.example>
      Archive: yes; filename*=iso-8859-1'es'ma=F1ana.txt

        NOTE: The raw use of non-ASCII character sets or of encodings
        other than those described above is not compliant with this
        standard, even though such usage has been seen in some
        hierarchies (with no indication of which character set has been
        used beyond the user's ability to guess based upon other clues
        in the article, or custom within the newsgroup). Future
        extensions to this standard may make provision for other
        character sets, hence the requirement that octets beyond the
        US-ASCII range be transported without error.

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4.4.2.  Character Sets within Article Bodies

   Within article bodies, characters are represented as octets according
   to the encoding scheme implied by any Content-Transfer-Encoding- and
   Content-Type-headers [RFC 2045].  In the absence of such headers,
   reading agents cannot be relied upon to display correctly more than
   the US-ASCII characters, though they MUST display at least those.

        NOTE: The use of non-ASCII characters in the absence of an
        appropriate Content-Type-header is not compliant with this
        standard, even though such usage has been seen in some
        hierarchies (with no indication of which character set has been
        used beyond the user's ability to guess based upon other clues
        in the article, or custom within the newsgroup).

   Followup agents MUST be careful to apply appropriate encodings to the
   outbound followup. A followup to an article containing non-ASCII
   material is very likely to contain non-ASCII material itself.

4.5.  Size Limits

   Compliant software MUST support headers of at least 998 octets, and
   that is the only limit on the length of a header line prescribed by
   this standard.  However, specific rules to the contrary may apply in
   particular cases (for example, according to [RFC 2047] header lines
   containing encoded-words are limited to 76 octets).

        NOTE: There is NO restriction on the number of lines into which
        a header may be split, and hence there is NO restriction on the
        total length of a header (in particular it may, by suitable
        folding, be made to exceed the 998 octets restriction pertaining
        to a single header line).

   The syntax provides for the lines of a body to be up to 998 octets in
   length, not including the CRLF. All software compliant with this
   standard MUST support lines of at least that length, both in headers
   and in bodies, and all such software SHOULD support lines of
   arbitrary length. In particular, relaying agents MUST transmit lines
   of arbitrary length without truncation or any other modification.

        NOTE: The limit of 998 octets is consistent with the
        corresponding limit in [RFC 2822].

        NOTE: This standard provides no upper bound on the overall size
        of a single article, but neither does it forbid relaying agents
        from dropping articles of excessive length. It is, however,
        suggested that any limits thought appropriate by particular
        agents would be more appropriately expressed in megabytes than
        in kilobytes.

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4.6.  Example

   Here is a sample article:

      Path: server.example/unknown.site2.example@site2.example/
      Newsgroups: example.announce,example.chat
      Message-ID: <9urrt98y53@site1.example>
      From: Ann Example <a.example@site1.example>
      Subject: Announcing a new sample article.
      Date: Wed, 27 Mar 2002 12:12:50 +0300
      Approved: example.announce moderator <jsmith@site.example>
      Followup-To: example.chat
      Reply-To: Ann Example <a.example+replies@site1.example>
      Expires: Mon, 22 Apr 2002 12:12:50 +0300
      Organization: Site1, The Number one site for examples.
      User-Agent: ExampleNews/3.14 (Unix)
      Keywords: example, announcement, standards, RFC 1036, Usefor
      Summary: The URL for the next standard.
      Injector-Info: injector.site.example; posting-host=du003.site.example
      Complaints-To: abuse@site.example

      Just a quick announcement that a new standard example article has
      been released; it is in the new USEFOR standard obtainable from

      Ann Example <a.example@site1.example>   Sample Poster to the Stars
      "The opinions in this article are bloody good ones" - J. Clarke.
[The RFC Editor is invited to change the above Date and Expires headers
to match the actual publication dates and to insert its correct URL.]

5.  Mandatory Headers

   An article MUST have one, and only one, of each of the following
   headers: Date, From, Message-ID, Subject, Newsgroups, Path.

   Note also that there are situations, discussed in the relevant parts
   of section 6, where References-, Sender-, or Approved-headers are
   mandatory. In control messages, specific values are required for
   certain headers.

   A proto-article (see 8.2.1) may lack some of these mandatory headers,
   but they MUST then be supplied by the injecting agent.

5.1.  Date

   The Date-header contains the date and time that the article was
   prepared by the poster ready for transmission and SHOULD express the
   poster's local time. The content syntax makes use of syntax defined
   in [RFC 2822] (but see the revised definition of zone in section

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      header              =/ Date-header
      Date-header         = "Date" ":" SP Date-content
      Date-content        = date-time

   The date-time MUST be semantically valid as required by [RFC 2822].
   Although folding white space is permitted throughout the date-time
   syntax, it is RECOMMENDED that a single space be used in each place
   that FWS appears (whether it is required or optional).

   In order to prevent the reinjection of expired articles into the news
   stream, relaying and serving agents MUST refuse "stale" articles
   whose Date-header predates the earliest articles of which they
   normally keep record, or which is more than 24 hours into the future
   (though they MAY use a margin less than that 24 hours). Relaying
   agents MUST NOT modify the Date-header in transit.

5.1.1.  Examples

      Date: Sat, 26 May 2001 11:13:00 -0500 (EST)
      Date: 26 May 2001 16:13 +0000
      Date: 26 May 2001 16:13 GMT (Obsolete)

5.2.  From

   The From-header contains the email address(es), possibly including
   the full name(s), of the article's poster(s), or of the person or
   agent on whose behalf the article is posted (see the Sender-header,
   6.2).  The content syntax makes use of syntax defined in [RFC 2822].

      header              =/ From-header
      From-header         = "From" ":" SP From-content
      From-content        = mailbox-list

        NOTE: Observe that there is no provision for parameters in this
        header, or in other headers containing addresses likely to be
        used for sending email (see 4.2.2).  When, for whatever reason,
        a poster does not wish to use a valid address, the mailbox
        concerned SHOULD end in the top level domain ".invalid" [RFC

5.2.1.  Examples:

      From: John Smith <jsmith@site.example>
      From: "John Smith" <jsmith@site.example>, dave@isp.example
      From: "John D. Smith" <jsmith@site.example>, andrew@isp.example,
      From: Jan Jones <jan@please_setup_your_system_correctly.invalid>
      From: Jan Jones <joe@guess-where.invalid>
      From: dave@isp.example (Dave Smith)

        NOTE: the last example shows a now deprecated convention of
        putting a poster's full name in a comment following the mailbox,
        rather than in a phrase at the start of it. Observe also the use
        of the quoted-string "John D. Smith" which is required on

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        account of presence of the '.' character.

5.3.  Message-ID

   The Message-ID-header contains the article's message identifier, a
   unique identifier distinguishing the article from every other
   article. The content syntax makes use of syntax defined in [RFC 2822]
   (but see the revised definition of msg-id in section 2.4.2).

      header             =/ Message-ID-header
      Message-ID-header  = "Message-ID" ":" SP Message-ID-content
      Message-ID-content = [FWS] msg-id [FWS]

   The msg-id MUST NOT be more than 250 octets in length.

        NOTE: The length restriction ensures that systems which accept
        message identifiers as a parameter when retrieving an article
        (e.g. [NNTP]) can rely on a bounded length. Observe that msg-id
        includes the '<' and '>'.

        Observe that, in contrast to the corresponding header in [RFC
        2822], the syntax does not allow comments within the Message-
        ID-header; this is to simplify processing by relaying and
        serving agents and to ensure interoperability with existing

   An agent generating an article's message identifier MUST ensure that
   it is unique (as also required in [RFC 2822]) and that it is chosen
   in such a way that it will NEVER be applied to any other Netnews
   article or Email message. However, an article emailed (without
   encapsulation) to a moderator (8.2.2 and 8.7) or gatewayed into some
   other medium (8.8.1) SHOULD retain the same message identifier
   throughout its travels so long as it remains recognizably the same

   Even though commonly derived from the domain name of the originating
   site (and domain names are case-insensitive), a message identifier
   MUST NOT be altered in any way during transport, or when copied (as
   into a References-header), and thus a simple (case-sensitive)
   comparison of octets will always suffice to recognize that same
   message identifier wherever it subsequently reappears.

        NOTE: These requirements are to be contrasted with those of the
        un-normalized msg-ids defined by [RFC 2822], which may perfectly
        legitimately become normalized (or vice versa) during transport
        or copying in email systems.

        NOTE: Some old software may treat message identifiers that
        differ only in case within their id-right part as equivalent,
        and implementors of agents that generate message identifiers
        should be aware of this.

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5.4.  Subject

   The Subject-header contains a short string identifying the topic of
   the message. This is an inheritable header (, normally to be
   copied into the Subject-header of any followup with the possible
   addition of a back-reference as described in B.6.

      header              =/ Subject-header
      Subject-header      = "Subject" ":" SP Subject-content
      Subject-content     = unstructured

        NOTE: The syntax of unstructured differs from that prescribed in
        [RFC 2822], so ensuring that the Subject-content is not
        permitted to be completely empty, or to consist of WSP only (see
        remarks in 4.2.6 concerning undesirable headers).

5.5.  Newsgroups

   The Newsgroups-header's content specifies the newsgroup(s) in which
   the article is intended to appear. It is an inheritable header
   ( which then becomes the default Newsgroups-header of any
   followup, unless a Followup-To-header is present to prescribe
   otherwise (see 8.6).  Articles MUST NOT be passed between relaying
   agents or to serving agents unless the sending agent has been
   configured to supply and the receiving agent to receive at least one
   of the newsgroup-names in the Newsgroups-header.

      header              =/ Newsgroups-header
      Newsgroups-header   = "Newsgroups"  ":" SP Newsgroups-content
                                    *( ";" extension-parameter )
      Newsgroups-content  = [FWS] newsgroup-name
                               *( [FWS] ng-delim [FWS] newsgroup-name )
      newsgroup-name      = component *( "." component )
      component           = 1*component-grapheme
      ng-delim            = ","
      component-grapheme  = DIGIT / ALPHA / "+" / "-" / "_"
[Maybe some better word for 'grapheme'.]

        NOTE: Observe that the syntax does not allow comments within the
        Newsgroups-header; this is to simplify processing by relaying
        and serving agents which have a requirement to process this
        header extremely rapidly.

   Components beginning with underline ("_") are reserved for use by
   future versions of this standard and MUST NOT occur in newsgroup-
   names (whether in Newsgroups-headers or in newgroup control messages
   (7.2.1)).  However, such names MUST be accepted.

   Components beginning with "+" or "-" are reserved for use by
   implementations and MUST NOT occur in newsgroup-names (whether in
   Newsgroups-headers or in newgroup control messages). Implementors may
   assume that this rule will not change in any future version of this

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        NOTE: For example, implementors may safely use leading "+" and
        "-" to "escape" other entities within something that looks like
        a newsgroup-name.

   The format of newsgroup-names is ultimately determined by the
   policies of those administrative agencies which have the
   responsibility for creating new newsgroups within the various
   hierarchies of Usenet. There are traditional, social and technical
   arguments why there should be restrictions on these formats (and the
   force of the technical ones changes over time with developments in
   computers and operating systems) Therefore, such administrative
   agencies SHOULD establish and promulgate the restrictions they intend
   to apply within their own hierarchies.

        NOTE: These issues are discussed more fully in [USEAGE].  The
        following policy restrictions represent what is considered safe
        and appropriate at the present time. Although purely advisory,
        hierarchy administrators should consider the consequences
        carefully before allowing them to be exceeded. They could also
        be taken as the defaults in unmanaged hierarchies.

        1. Uppercase letters are forbidden.

        2. A component name is forbidden to consist entirely of digits.

        3. A component is limited to 30 component-graphemes and a
           newsgroup-name to 71 component-graphemes (counting also the
           '.'s separating the components).
[There was a suggestion to reduce that 71 to 66 in order to allow such a
newsgoup-name to fit in the on the first line of a Followup-To-header
without exceeding 79 characters.]

   Serving and relaying agents MUST accept any syntactially correct
   newsgroup-name even if it would violate whatever policy restrictions
   may be in place. Posting and injecting agents MAY enforce them (but
   only with the explicit agreement of the poster).

   The inclusion of folding white space within a Newsgroups-content is a
   newly introduced feature in this standard. It MUST be accepted by all
   conforming implementations (relaying agents, serving agents and
   reading agents).  Posting agents should be aware that such postings
   may be rejected by overly-critical old-style relaying agents. When a
   sufficient number of relaying agents are in conformance, posting
   agents SHOULD generate such whitespace in the form of <CRLF WSP> so
   as to keep the length of lines in the relevant headers (notably
   Newsgroups and Followup-To) to a reasonable length (such as 79
   characters, which is likely to be displayed satisfactorily by most
   current reading agents).  Before such critical mass occurs, injecting
   agents MAY reformat such headers by removing whitespace inserted by
   the posting agent, but relaying agents MUST NOT do so.

   Posters SHOULD use only the names of existing newsgroups in the
   Newsgroups-header. However, it is legitimate to cross-post to
   newsgroups which do not exist on the posting agent's host, provided

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   that at least one of the newsgroups DOES exist there. Relaying agents
   MUST NOT rewrite Newsgroups-headers in any way, even if some or all
   of the newsgroups do not exist on the relaying agent's host. Serving
   agents MUST NOT create new newsgroups simply because an unrecognized
   newsgroup-name occurs in a Newsgroups-header (see 7.2.1 for the
   correct method of newsgroup creation).

   The Newsgroups-header is intended for use in Netnews articles rather
   than in email messages. It MAY be used in an email message to
   indicate that it is a copy also posted to the listed newsgroups, in
   which case the inclusion of a Posted-And-Mailed header (6.9) would
   also be appropriate. However, it SHOULD NOT be used in an email-only
   reply to a Netnews article (thus the "inheritable" property of this
   header applies only to followups to a newsgroup, and not to followups
   to the poster).

5.5.1.  Forbidden newsgroup-names

   The following forms of newsgroup-name MUST NOT be used except for the
   specific purposes indicated:

     o Newsgroup-names having only one component. These are reserved for
       newsgroups whose propagation is restricted to a single host or
       local network, and for pseudo-newsgroups such as "poster" (which
       has special meaning in the Followup-To-header - see section 6.7),
       "junk" (often used by serving agents), and "control" (likewise);
     o Any newsgroup-name beginning with "control." (used as pseudo-
       newsgroups by many serving agents);
     o Any newsgroup-name containing the component "ctl" (likewise);
     o "to" or any newsgroup-name beginning with "to." (reserved for the
       ihave/sendme protocol described in section 7.4, and for test
       messages sent on an essentially point-to-point basis);
     o Any newsgroup-name beginning with "example." (reserved for
       examples in this and other standards);
     o Any newsgroup-name containing the component "all" (because this
       is used as a wildcard in some implementations).

   A newsgroup-name SHOULD NOT appear more than once in the Newsgroups-
   header.  The order of newsgroup-names in the Newsgroups-header is not
   significant, except for determining which moderator to send the
   article to if more than one of the groups is moderated (see 8.2).

5.6.  Path

   The Path-header shows the route taken by a message since its entry
   into the Netnews system. It is a variant header (, each agent
   that processes an article being required to add one (or more) entries
   to it. This is primarily to enable relaying agents to avoid sending
   articles to sites already known to have them, in particular the site
   they came from, and additionally to permit tracing the route articles
   take in moving over the network, and for gathering Usenet statistics.
   Finally the presence of a '%' path-delimiter in the Path-header can
   be used to identify an article injected in conformance with this

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5.6.1.  Format

      header          =/ Path-header
      Path-header     = "Path" ":" SP Path-content
                           *( ";" extension-parameter )
      Path-content    = [FWS]
                           *( path-identity [FWS] path-delimiter [FWS] )
                           tail-entry [FWS]
      path-identity   = ( ALPHA / DIGIT )
                           *( ALPHA / DIGIT / "-" / "." / ":" / "_" )
      path-delimiter  = "/" / "?" / "%" / "," / "!"
      tail-entry      = path-identity

        NOTE: A Path-content will inevitably contain at least one path-
        identity, except possibly in the case of a proto-article that
        has not yet been injected onto the network.

        NOTE: Observe that the syntax does not allow comments within the
        Path-header; this is to simplify processing by relaying and
        injecting agents which have a requirement to process this header
        extremely rapidly.

   A relaying agent SHOULD NOT pass an article to another relaying agent
   whose path-identity (or some known alias thereof) already appears in
   the Path-content. Since the comparison may be either case sensitive
   or case insensitive, relaying agents SHOULD NOT generate a name which
   differs from that of another site only in terms of case.

   A relaying agent MAY decline to accept an article if its own path-
   identity is already present in the Path-content or if the Path-
   content contains some path-identity whose articles the relaying agent
   does not want, as a matter of local policy.

        NOTE: This last facility is sometimes used to detect and decline
        control messages (notably cancel messages) which have been
        deliberately seeded with a path-identity to be "aliased out" by
        sites not wishing to act upon them.

5.6.2.  Adding a path-identity to the Path-header

   When an injecting, relaying or serving agent receives an article, it
   MUST prepend its own path-identity followed by a path-delimiter to
   the beginning of the Path-content. In addition, it SHOULD then add
   CRLF and WSP if it would otherwise result in a line longer than 79

   The path-identity added MUST be unique to that agent. To this end it
   SHOULD be one of:

   1. A fully qualified domain name (FQDN) associated (by the Internet
      DNS service [RFC 1034]) with an A record, which SHOULD identify
      the actual machine prepending this path-identity. Ideally, this
      FQDN should also be "mailable" (see below).

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   2. A fully qualified domain name (FQDN) associated (by the Internet
      DNS service) with an MX record, which MUST be "mailable".

   3. An arbitrary name believed to be unique and registered at least
      with all sites immediately downstream from the given site.

   4. An encoding of an IP address - <IPv4address> or <IPv6address> [RFC
      2373] (the requirement to be able to use an <IPv6address> is the
      reason for including ':' as an allowed character within a path-

   The FQDN of an agent is "mailable" if the administrators of that
   agent can be reached by email using both of the forms "usenet@<FQDN>"
   and "news@<FQDN>", in conformity with [RFC 2142].

   Of the above options, nos. 1 to 3 are much to be preferred, unless
   there are strong technical reasons dictating otherwise. In
   particular, the injecting agent's path-identity MUST, as a special
   case, be an FQDN as in option 1 or option 2, and MUST be mailable.
   Additionally, in the case of an injecting agent offering its services
   to the general public, its administrators MUST also be reachable
   using the form "abuse@<FQDN>" UNLESS a more specific complaints
   address has been specified in a Complaints-To-header (6.20).

   The injecting agent's path-identity MUST be followed by the special
   path-delimiter '%' which serves to separate the pre-injection and
   post-injection regions of the Path-content (see 5.6.3).

   In the case of a relaying or serving agent, the path-delimiter is
   chosen as follows.  When such an agent receives an article, it MUST
   establish the identity of the source and compare it with the leftmost
   path-identity of the Path-content. If it matches, a '/' should be
   used as the path-delimiter when prepending the agent's own path-
   identity.  If it does not match then the agent should prepend two
   entries to the Path-content; firstly the true established path-
   identity of the source followed by a '?'  path-delimiter, and then,
   to the left of that, the agent's own path-identity followed by a '/'
   path-delimiter as usual.  This prepending of two entries SHOULD NOT
   be done if the provided and established identities match.

   Any method of establishing the identity of the source may be used
   (but see 5.6.5 below), with the consideration that, in the event of
   problems, the agent concerned may be called upon to justify it.

        NOTE: The use of the '%' path-delimiter marks the position of
        the injecting agent in the chain. In normal circumstances there
        should therefore be only one '%' path-delimiter present, and
        injecting agents MAY choose to reject proto-articles with a '%'
        already in them. If, for whatever reason, more than one '%' is
        found, then the path-identity in front of the leftmost '%' is to
        be regarded as the true injecting agent.

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5.6.3.  The tail-entry

   For historical reasons, the tail-entry (i.e. the rightmost entry in
   the Path-content) is regarded as a "user name", and therefore MUST
   NOT be interpreted as a site through which the article has already
   passed. Moreover, the Path-content as a whole is not an email address
   and MUST NOT be used to contact the poster. Posting and/or injecting
   agents MAY place any string here.  When it is not an actual user
   name, the string "not-for-mail" is often used, but in fact a simple
   "x" would be sufficient.

   Often this field will be the only entry in the region (known as the
   pre-injection region) after the '%', although there may be entries
   corresponding to machines traversed between the posting agent and the
   injecting agent proper. In particular, injecting agents that receive
   articles from many sources MAY include information to establish the
   circumstances of the injection such as the identity of the source
   machine (especially if an Injector-Info-header (6.19) is not being
   provided). Any such inclusion SHOULD NOT conflict with any genuine
   site identifier. The '!'  path-delimiter may be used freely within
   the pre-injection region, although '/' and '?' are also appropriate
   if used correctly.

5.6.4.  Path-Delimiter Summary

   A summary of the various path-delimiters. The name immediately to the
   left of the path-delimiter is always that of the machine which added
   the path-delimiter.

   '/' The name immediately to the right is known to be the identity of
       the machine from which the article was received (either because
       the entry was made by that machine and we have verified it, or
       because we have added it ourselves).

   '?' The name immediately to the right is the claimed identity of the
       machine from which the article was received, but we were unable
       to verify it (and have prepended our own view of where it came
       from, and then a '/').

   '%' Everything to the right is the pre-injection region followed by
       the tail-entry.  The name on the left is the FQDN of the
       injecting agent. The presence of two '%'s in a path indicates a
       double-injection (see 8.2.2).

   '!' The name immediately to the right is unverified. The presence of
       a '!' to the left of the '%' indicates that the identity to the
       left is that of an old-style system not conformant with this

   ',' Reserved for future use, treat as '/'.

       Old software may possibly use other path-delimiters, which should
       be treated as '!'.  But note in particular that ':', '-' and '_'

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       are components of names, not path-delimiters, and FWS on its own
       MUST NOT be used as the sole path-delimiter.

        NOTE: Old Netnews relaying and injecting agents almost all
        delimit Path entries with a '!', and these entries are not
        verified.  The presence of '%' indicates that the article was
        injected by software conforming to this standard, and the
        presence of '!' to the left of a '%' indicates that the message
        passed through systems developed prior to this standard. It is
        anticipated that relaying agents will reject articles in the old
        style once this new standard has been widely adopted.

5.6.5.  Suggested Verification Methods

[Section now omitted.]

5.6.6.  Example

      Path: foo.isp.example/

        NOTE: That article was injected into the news stream by
        baz.isp.example (complaints may be addressed to
        abuse@baz.isp.example). The injector has taken care to record
        that it got it from dialup123.baz.isp.example. "x" is a dummy
        tail-entry, though sometimes a real userid is put there.

        The article was relayed, perhaps by UUCP, to the machine known,
        at least to its downstream, as "barbaz".

        Barbaz relayed it to old.site.example, which does not yet
        conform to this standard (hence the '!' path-delimiter). So one
        cannot be sure that it really came from barbaz.

        Old.site.example relayed it to a site claiming to have the IP
        address [], and claiming (by using the '/' path-
        delimiter) to have verified that it came from old.site.example.

        [] relayed it to "foo-server" which, not being
        convinced that it truly came from [], did a reverse
        lookup on the actual source and concluded it was known as
        bar.isp.example (that is not to say that [] was not a
        correct IP address for bar.isp.example, but simply that that
        connection could not be substantiated by foo-server).  Observe
        that foo-server has now added two entries to the Path.

        "foo-server" is a locally significant name within the complex
        site of many machines run by foo.isp.example, so the latter
        should have no problem recognizing foo-server and using a '/'
        path-delimiter.  Presumably foo.isp.example then delivered the
        article to its direct clients.

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        It appears that foo.isp.example and old.site.example decided to
        fold the line, on the grounds that it seemed to be getting a
        little too long.

6.  Optional Headers

   None of the headers appearing in this section is required to appear
   in every article but some of them are required in certain types of
   article, such as followups. Any header defined in this (or any other)
   standard MUST NOT appear more than once in an article unless
   specifically stated otherwise.  Experimental headers ( and
   headers defined by cooperating subnets are exempt from this
   requirement.  See section 8 "Duties of Various Agents" for the full

6.1.  Reply-To

   The Reply-To-header specifies a reply address(es) to be used for
   personal replies for the poster(s) of the article when this is
   different from the poster's address(es) given in the From-header. The
   content syntax makes use of syntax defined in [RFC 2822].

      header              =/ Reply-To-header
      Reply-To-header     = "Reply-To" ":" SP Reply-To-content
      Reply-To-content    = address-list

   In the absence of Reply-To, the reply address(es) is the address(es)
   in the From-header.

6.1.1.  Examples

      Reply-To: John Smith <jsmith@site.example>
      Reply-To: John Smith <jsmith@site.example>, dave@isp.example
      Reply-To: John Smith <jsmith@site.example>,andrew@isp.example,

6.2.  Sender

   The Sender-header specifies the mailbox of the person or entity which
   caused this article to be posted (and hence injected), if that person
   or entity is different from that given in the From-header or if more
   than one mailbox appears in the From-header. This header SHOULD NOT
   appear in an article unless the sender is different from the poster.
   This header is appropriate for use by automatic article posters. The
   content syntax makes use of syntax defined in [RFC 2822].

      header              =/ Sender-header
      Sender-header       = "Sender" ":" SP Sender-content
      Sender-content      = mailbox

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6.3.  Organization

   The Organization-header is a short phrase identifying the poster's

      header              =/ Organization-header
      Organization-header = "Organization" ":" SP Organization-content
      Organization-content= unstructured

6.4.  Keywords

   The Keywords field contains a comma separated list of important words
   and phrases intended to describe some aspect of the content of the
   article. The content syntax makes use of syntax defined in [RFC

      header              =/ Keywords-header
      Keywords-header     = "Keywords" ":" SP Keywords-content
      Keywords-content    = phrase *( "," phrase )

        NOTE: The list is comma separated, NOT space separated.

        NOTE: Contrary to the usage defined in [RFC 2822], this standard
        does not permit multiple occurrences of this header.

6.5.  Summary

   The Summary-header is a short phrase summarizing the article's

      header              =/ Summary-header
      Summary-header      = "Summary" ":" SP Summary-content
      Summary-content     = unstructured

6.6.  Distribution

   The Distribution-header is an inheritable header (see which
   specifies geographical or organizational limits to an article's

      header              =/ Distribution-header
      Distribution-header = "Distribution" ":" SP Distribution-content
                               *( ";" extension-parameter )
      Distribution-content= distribution *( dist-delim distribution )
      dist-delim          = ","
      distribution        = [FWS] distribution-name [FWS]
      distribution-name   = ALPHA 1*distribution-rest
      distribution-rest   = ALPHA / "+" / "-" / "_"

   Articles MUST NOT be passed between relaying agents or to serving
   agents unless the sending agent has been configured to supply and the
   receiving agent to receive at least one of the distributions in the
   Distribution-header.  Additionally, reading agents MAY also be
   configured so that unwanted distributions do not get displayed.

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        NOTE: Although it would seem redundant to filter out unwanted
        distributions at both ends of a relaying link (and it is clearly
        more efficient to do so at the sending end), many sending sites
        have been reluctant, historically speaking, to apply such
        filters (except to ensure that distributions local to their own
        site or cooperating subnet did not escape); moreover they tended
        to configure their filters on an "all but those listed" basis,
        so that new and hitherto unheard of distributions would not be
        caught. Indeed many "hub" sites actually wanted to receive all
        possible distributions so that they could feed on to their
        clients in all possible geographical (or organizational)

        Therefore, it is desirable to provide facilities for rejecting
        unwanted distributions at the receiving end. Indeed, it may be
        simpler to do so locally than to inform each sending site of
        what is required, especially in the case of specialized
        distributions (for example for control messages, such as cancels
        from certain issuers) which might need to be added at short
        notice.  The possibility for reading agents to filter
        distributions has been provided for the same reason.

   Exceptionally, ALL relaying agents are deemed willing to supply or
   accept the distribution "world", and NO relaying agent should supply
   or accept the distribution "local".  However, "world" SHOULD NEVER be
   mentioned explicitly since it is the default when the Distribution-
   header is absent entirely.  "All" MUST NOT be used as a
   distribution-name.  Distribution-names SHOULD contain at least three
   characters, except when they are two-letter country names as in [ISO
   3166].  Distribution-names are case-insensitive (i.e. "US", "Us" and
   "us" all specify the same distribution).

   Followup agents SHOULD initially supply the same Distribution-header
   as found in the precursor.

6.7.  Followup-To

   The Followup-To-header specifies which newsgroup(s) followups should
   be posted to.

      header              =/ Followup-To-header
      Followup-To-header  = "Followup-To" ":" SP Followup-To-content
                               *( ";" extension-parameter )
      Followup-To-content = Newsgroups-content /
                            [FWS] %x70.6F. [FWS]
                            ; which is a case-sensitive "poster"

   The syntax is the same as that of the Newsgroups-content, with the
   addition that the keyword "poster" is allowed. In the absence of a
   Followup-To-content, the default newsgroup(s) for a followup are
   those in the Newsgroups-header.

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   A Followup-To-header consisting of the keyword "poster" indicates
   that the poster requests no followups to be sent in response to this
   article, only personal replies to the article's reply address.
   Although the keyword "poster" is case-sensitive, followup agents MAY
   choose to regognize case insensitive forms such as "Poster".

        NOTE: A poster who wishes both  a personal reply and a followup
        post should include an appropriate Mail-Copies-To-header (6.8).

6.8.  Mail-Copies-To

   The Mail-Copies-To-header indicates whether or not the poster wishes
   to have followups to an article emailed in addition to being posted
   to Netnews and, if so, establishes the address to which they should
   be sent.

   The content syntax makes use of syntax defined in [RFC 2822].

      header      =/ Mail-Copies-To-header
                  = "Mail-Copies-To" ":" SP Mail-Copies-To-content
                  = copy-addr / [CFWS] ( "nobody" / "poster" ) [CFWS]
      copy-addr   = address-list

   The keyword "nobody" indicates that the poster does not wish copies
   of any followup postings to be emailed. This indication is widely
   seen as a very strong wish, and is to be taken as the default when
   this header is absent.

   The keyword "poster" indicates that the poster wishes a copy of any
   followup postings to be emailed to him.

   Otherwise, this header contains a copy-addr to which the poster
   wishes a copy of any followup postings to be sent.

        NOTE: Some existing practice uses the keyword "never" in place
        of "nobody" and "always" in place of "poster". These usages are
        deprecated, but followup agents MAY observe them.  The actions
        to be taken by by followup agent when following up to an article
        containing a Mail-Copies-To header are set out in section 8.6.

   Whether or not this header will also find similar usage for replies
   to messages sent to mailing lists falls outside the scope of this

6.9.  Posted-And-Mailed

      header      =/ Posted-And-Mailed-header
                  = "Posted-And-Mailed" ":" SP Posted-And-Mailed-content
                       *( ";" extension-parameter )
                  = [CFWS] ( "yes" / "no" ) [CFWS]

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   This header, when used with the "yes" keyword, indicates that the
   article has been both posted to the specified newsgroups and emailed.
   It SHOULD be used when replying to the poster of an article to which
   this one is a followup (see the Mail-Copies-To-header in section 6.8)
   and it MAY be used when any article is also mailed to a recipient(s)
   identified in a To- and/or Cc-header that is also present. The "no"
   keyword is included for the sake of completeness; it MAY be used to
   indicate the opposite state, but is redundant insofar as it only
   describes the default state when this header is absent.

   This header, if present, MUST be included in both the posted and
   emailed versions of the article. The Newsgroups-header of the posted
   article SHOULD be included in the email version as recommended in
   section 5.5.  All other headers defined in this standard (excluding
   variant headers) MUST be identical in both the posted and mailed
   versions of the article.  The bodies MUST be identical in both, apart
   from a possible change of Content-Transfer-Encoding.

        NOTE: This leaves open the question of whether a To- or a Cc-
        header should appear in the posted version. Naturally, a Bcc-
        header should not appear, except in a form which indicates that
        there are additional unspecified recipients.

6.10.  References

   The References-header is an inheritable header (see which
   lists CFWS-separated message identifiers of the article's precursors,
   as described in 8.6.  The content syntax makes use of syntax defined
   in [RFC 2822] (but see the revised definition of msg-id in section

      header              =/ References-header
      References-header   = "References" ":" SP References-content
      References-content  = [CFWS] msg-id *( CFWS msg-id ) [CFWS]

        NOTE: This differs from the syntax of [RFC 2822] by requiring at
        least one CFWS between the msg-ids (a SP at this point was an
        [RFC 1036] requirement).

   A followup MUST have a References-header, and an article that is not
   a followup MUST NOT have a References-header.

6.10.1.  Examples

      References: <i4g587y@site1.example>
      References: <i4g587y@site1.example> <kgb2231+ee@site2.example>
      References: <i4g587y@site1.example> <kgb2231+ee@site2.example>
         <222@site1.example> <87tfbyv@site7.example>
      References: <i4g587y@site1.example> <kgb2231+ee@site2.example>

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6.11.  Expires

   The  Expires-header specifies a date and time when the article is
   deemed to be no longer relevant and  could usefully  be removed
   ("expired"). The content syntax makes use of syntax defined in [RFC

      header              =/ Expires-header
      Expires-header      = "Expires" ":" SP Expires-content
                               *( ";" extension-parameter )
      Expires-content     = date-time

        NOTE: This header is suitable for specifying both unusually
        short and unusually long expiry times; there is little point in
        using it in other circumstances.

6.12.  Archive

   This optional header provides an indication of the poster's intent
   regarding preservation of the article in publicly accessible long-
   term or permanent storage.

      header              =/ Archive-header
      Archive-header      = "Archive" ":" SP Archive-content
                               *( ";" ( Archive-parameter /
                                        extension-parameter ) )
      Archive-content     = [CFWS] ("no" / "yes" ) [CFWS]
      Archive-parameter   = <a parameter with attribute "filename"
                             and any value>

   The presence of an "Archive: no" header in an article indicates that
   the poster does not permit redistribution from publicly accessible
   long-term or permanent archives. The absence of this header, or an
   explicit "Archive: yes", indicates that the poster is willing for
   such redistribution to take place.  The optional "filename" parameter
   can then be used to suggest a filename under which the article should
   be stored. Further extensions to this standard may provide additional
   parameters for administration of the archiving process.

        NOTE: This standard does not attempt to define the length of
        "long-term", since it is dependent on many factors, including
        the retention policies of individual sites, and the customs or
        policies established for particular newsgroups or hierarchies.

        NOTE: Posters are cautioned that some sites may not implement
        the "no" option of the Archive-header correctly. In some
        jurisdictions non-compliance with this header may constitute a
        breach of copyright or of other legal provisions.  Moreover,
        even if this header prevents the poster's words from being
        archived publicly, it does nothing to prevent the archiving of a
        followup in which those words are quoted.

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6.13.  Control

   The Control-header marks the article as a control message, and
   specifies the desired actions (additional to the usual ones of
   storing and/or relaying the article).

      header              =/ Control-header
      Control-header      = "Control" ":" SP Control-content
                               *( ";" extension-parameter )
      Control-content     = [CFWS] control-message [CFWS]
      control-message     = <empty>

   However, the rule given above for control-message is incomplete.
   Further alternatives will be added incrementally as the various
   control-messages are introduced in section 7, or in extensions to
   this standard, using the "=/" notation defined in [RFC 2234].  For
   example, a putative Control-message would be defined as follows:

      control-message     =/ Control-message
      Control-message     = "Control" Control-arguments
      Control-arguments   = <the argument(s) specific to that

   where "Control" is a "verb" which is (and MUST be) of the syntactic
   form of a token and Control-arguments MUST be of the syntactic form
   of a CFWS-separated list of values (which may require the use of
   quoted-strings if any tspecials or non-ASCII characters are

   The verb indicates what action should be taken, and the argument(s)
   (if any) supply details. In some cases, the body of the article may
   also contain details.

   An article with a Control-header MUST NOT also have a Supersedes-

        NOTE: The presence of a Subject-header starting with the string
        "cmsg " and followed by a Control-message MUST NOT be construed,
        in the absence of a proper Control-header, as a request to
        perform that control action (as may have occurred in some legacy

6.14.  Approved

   The Approved-header indicates the mailing addresses (possibly
   including the full names) of the persons or entities approving the
   article for posting.

      header              =/ Approved-header
      Approved-header     = "Approved" ":" SP Approved-content
                               *( ";" extension-parameter )
      Approved-content    = From-content  ; see 5.2

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   Each mailbox contained in the Approved-content MUST be that of one of
   the person(s) or entity(ies) in question, and one of those mailboxes
   MUST be that of the actual injector of the article.

   An Approved-header is required in all postings to moderated
   newsgroups. If this header is not present in such postings, then
   serving agents MUST (and relaying agents MAY) reject the article.
   Please see section 8.2.2 for how injecting agents should treat
   postings to moderated groups that do not contain this header.

   An Approved-header is also required in certain control messages, to
   reduce the risks of accidental or unauthorized posting of same.

        NOTE: The presence of an Approved-header indicates that the
        person or entity identified claims to have the necessary
        authority to post the article in question, thus enabling sites
        that dispute that authority to refuse to accept or to act upon
        it. However, the mere presence of the header is insufficient to
        provide assurance that it indeed originated from that person or
        entity, and it is therefore desirable that it be included within
        some digital signature scheme (see 7.1), especially in the case
        of control messages (section 7).

6.15.  Supersedes

   The Supersedes-header contains a message identifier specifying an
   article to be superseded upon the arrival of this one. The specified
   article MUST be treated as though a "cancel" control message had
   arrived for the article (but observe that a site MAY choose not to
   honour a "cancel" message, especially if its authenticity is in
   doubt). The content syntax makes use of syntax defined in [RFC 2822]
   (but see the revised definition of msg-id in section 2.4.2).

      header              =/ Supersedes-header
      Supersedes-header   = "Supersedes" ":" SP Supersedes-content
      Supersedes-content  = [CFWS] msg-id [CFWS]

        NOTE: There is no "c" in "Supersedes".

        NOTE: The Supersedes-header defined here has no connection with
        the Supersedes-header that sometimes appears in Email messages
        converted from X.400 according to [RFC 2156]; in particular, the
        syntax here permits only one msg-id in contrast to the multiple
        msg-ids in that Email version.

   Thus when an article contains a Supersedes-header, the old article
   mentioned SHOULD be withdrawn from circulation or access, as in a
   cancel message (7.3), and the new article inserted into the system as
   any other new article would have been.

   Whatever security or authentication checks are normally applied to a
   Control cancel message (or may be prescribed for such messages by
   some extension to this standard - see the remarks in 7.1 and 7.3)
   MUST also be applied to an article with a Supersedes-header. In the

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   event of the failure of such checks, the article SHOULD be discarded,
   or at most stored as an ordinary article.

6.16.  Xref

   The Xref-header is a variant header ( which indicates where
   an article was filed by the last serving agent to process it.

      header            =/ Xref-header
      Xref-header       = "Xref" ":" SP Xref-content
                             *( ";" extension-parameter )
      Xref-content      = [CFWS] server-name 1*( CFWS location ) [CFWS]
      server-name       = path-identity  ; see 5.6.1
      location          = newsgroup-name ":" article-locator
      article-locator   = 1*( %x21-27 / %x29-3A / %x3C-7E )
                             ; US-ASCII printable characters
                             ; except '(' and ';'

   The server-name is included so that software can determine which
   serving agent generated the header. The locations specify what
   newsgroups the article was filed under (which may differ from those
   in the Newsgroups-header) and where it was filed under them. The
   exact form of an article-locator is implementation-specific.

        NOTE: The traditional form of an article-locator is a decimal
        number, with articles in each newsgroup numbered consecutively
        starting from 1. NNTP demands that such a model be provided, and
        much other software expects it, but it seems desirable to permit
        flexibility for unorthodox implementations.

   An agent inserting an Xref-header into an article MUST delete any
   previous Xref-header(s). A relaying agent MAY delete it before
   relaying, but otherwise it SHOULD be ignored by any relaying or
   serving agent receiving it.

   It is convenient, though not required, for a serving agent to use the
   same server-name in Xref-headers as the path-identity it uses in
   Path-headers (just so long as reading agents can distinguish it from
   other serving agents known to them).

6.17.  Lines

   The Lines-header indicates the number of lines in the body of the

      header              =/ Lines-header
      Lines-header        = "Lines" ":" SP Lines-content
                               *( ";" extension-parameter )
      Lines-content       = [CFWS] 1*DIGIT [CFWS]

   The line count includes all body lines, including the signature if
   any, including empty lines (if any) at the beginning or end of the
   body, and including the whole of all MIME message and multipart parts
   contained in the body (the single empty separator line between the

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   headers and the body is not part of the body). The "body" here is the
   body as found in the posted article as transmitted by the posting

   This header is to be regarded as obsolete, and it will likely be
   removed entirely in a future version of this standard. In the
   meantime, its use is deprecated.

6.18.  User-Agent

   The User-Agent-header contains information about the user agent
   (typically a newsreader) generating the article, for statistical
   purposes and tracing of standards violations to specific software
   needing correction. Although not one of the mandatory headers,
   posting agents SHOULD normally include it. It is also intended that
   this header be suitable for use in Email.

      header              =/ User-Agent-header
      User-Agent-header   = "User-Agent" ":" SP User-Agent-content
                               *( ";" extension-parameter )
      User-Agent-content  = product *( CFWS product )
      product             = [CFWS] token [CFWS] [ "/" product-version ]
      product-version     = [CFWS] token [CFWS]

   This header MAY contain multiple product-tokens identifying the agent
   and any subproducts which form a significant part of the posting
   agent, listed in order of their significance for identifying the
   application. Product-tokens should be short and to the point - they
   MUST NOT be used for information beyond the canonical name of the
   product and its version.  Injecting agents MAY include product
   information for themselves (such as "INN/1.7.2"), but relaying and
   serving agents MUST NOT generate or modify this header to list

        NOTE: Minor variations from [RFC 2616] which describes a similar
        facility for the HTTP protocol:

        1. "{" and "}" are allowed in a token (product and product-
           version) in Netnews,

        2. Comments are permitted wherever whitespace is allowed.

        NOTE: This header supersedes the role performed redundantly by
        experimental headers such as X-Newsreader, X-Mailer, X-Posting-
        Agent, X-Http-User-Agent, and other headers previously used on
        Usenet and in Email for this purpose. Use of these experimental
        headers SHOULD be discontinued in favor of the single, standard

6.18.1.  Examples

      User-Agent: tin/1.3-950621beta-PL0 (Unix)
      User-Agent: tin/pre-1.4-971106 (UNIX) (Linux/2.0.30 (i486))
      User-Agent: Mozilla/4.02b7 (X11; I; en; HP-UX B.10.20 9000/712)

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      User-Agent: Microsoft-Internet-News/4.70.1161
      User-Agent: Gnus/5.4.64 XEmacs/20.3beta17 ("Bucharest")
      User-Agent: inn/1.7.2
      User-Agent: telnet

6.19.  Injector-Info

   The Injector-Info-header SHOULD be added to each article by the
   injecting agent in order to provide information as to how that
   article entered the Netnews system and to assist in tracing its true

      header          =/ Injector-Info-header
                      = "Injector-Info" ":" SP Injector-Info-content
                           *( ";" ( Injector-Info-parameter /
                                    extension-parameter ) )
                      = [CFWS] path-identity [CFWS]
                      = posting-host-parameter /
                        posting-account-parameter /
                        posting-sender-parameter /
                        posting-logging-parameter /
                        ; for {USENET}-parameters see 4.1
                      = <a parameter with attribute "posting-host"
                         and value some host-value>
      host-value      = dot-atom /
                        [ dot-atom ":" ]
                          ( IPv4address / IPv6address ); see [RFC 2373]
                      = <a parameter with attribute "posting-account"
                         and any value>
                      = <a parameter with attribute "sender"
                         and value some sender-value>
      sender-value    = mailbox / "verified"
                      = <a parameter with attribute "logging-data"
                         and any value>
                      = <a parameter with attribute "posting-date"
                         and value some date-time>

   An Injector-Info-header MUST NOT be added to an article by any agent
   other than an injecting agent. Any Injector-Info-header present when
   an article arrives at an injecting agent MUST be removed. In
   particular if, for some exceptional reason (8.2.2), an article gets
   injected twice, the Injector-Info-header will always relate to the
   second injection.

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   The path-identity MUST be the same as the path-identity prepended to
   the Path-header by that same injecting agent which, following section
   5.6.2, MUST therefore be a fully qualified domain name (FQDN)
   mailable address.

   Although comments and folding of white space are permitted throughout
   the Injector-Info-content specification, it is RECOMMENDED that
   folding is not used within any parameter (but only before or after
   the ";" separating those parameters), and that comments are only used
   following the last parameter. It is also RECOMMENDED that such
   parameters as are present are included in the order in which they
   have been defined in the syntax above.  An injecting agent SHOULD use
   a consistent form of this header for all articles emanating from the
   same or similar origins.

        NOTE: The effect of those recommendations is to facilitate the
        recognition of articles arising from certain designated origins
        (as in the so-called "killfiles" which are available in some
        reading agents). Observe that the order within the syntax has
        been chosen to place last those parameters which are most likely
        to change between successive articles posted from the same

        NOTE:  To comply with the overall "attribute = value" syntax of
        parameters, any value containing an IPv6address, a date-time, a
        mailbox, any UTF8-xtra-char, or any CFWS MUST be quoted using
        <DQUOTE>s (the quoting is optional in other cases).

        NOTE: This header is intended to replace various currently-used
        but nowhere-documented headers such as "NNTP-Posting-Host",
        "NNTP-Posting-Date" and "X-Trace". These headers are now
        deprecated, and any of them present when an article arrives at
        an injecting agent SHOULD also be removed as above.

6.19.1.  Usage of Injector-Info-parameters

   The purpose of these parameters is to enable the injecting agent to
   make assertions about the origin of the article, in fulfilment of its
   responsibilities towards the rest of the network as set out in
   section 8.2.

   An injecting agent MUST NOT include any Injector-Info-parameter
   unless it has positive evidence of its correctness. An injecting
   agent MAY also include extension-parameters with x-attributes which
   will assist in identifying the origin of the article.  The posting-host-parameter

   If a dot-atom is present, it MUST be a FQDN identifying the specific
   host from which the injecting agent received the article.
   Alternatively, an IP address (IPv4address or IPv6address) identifies
   that host. If both forms are present, then they MUST identify the
   same host, or at least have done so at the time the article was

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        NOTE: It is commonly the case that this parameter identifies a
        dial-up point-of-presence, in which case a posting-account or
        logging-data may need to be consulted to find the true origin of
        the article.  The posting-account-parameter

   This parameter identifies the source from which the injecting agent
   received the article. It SHOULD be in a cryptic notation
   understandable only by the administrator of the injecting agent, but
   it MUST be such that a given source gives rise to the same posting-
   account, at least in the short term. If the injecting agent is unable
   to meet that obligation, then it should use a posting-logging-
   parameter instead.  The posting-sender-parameter

   This parameter identifies the mailbox of the verified sender of the
   article (alternatively, it uses the token "verified" to indicate that
   at least any addr-spec in the Sender-header of the article, or in the
   From-header if the Sender-header is absent, is correct).

        NOTE: An injecting agent is unlikely to be able to make use of
        this parameter except in cases where it is running on a machine
        which is aware of the user-space in which the posting agent is
        operating. This parameter should be used in preference to a
        posting-account-parameter in such situations.  The posting-logging-parameter

   This parameter contains information (typically a session number or
   other non-persistent means of identifying a posting account) which
   will enable the true origin of the article to be determined by
   reference to logging information kept by the injecting agent.  The posting-date-parameter

   This parameter identifies the time at which the article was injected
   (as distinct from the Date-header, which indicates when it was

6.19.2.  Example

      Injector-Info: news2.isp.net; posting-host=modem-15.pop.isp.net;
         posting-account=client0002623; logging-data=2427;
         posting-date="Wed, 2 Aug 2000 20:05:33 +0100 (BST)"

6.20.  Complaints-To

   The Complaints-To-header is added to an article by an injecting agent
   in order to indicate the mailbox to which complaints concerning the
   poster of the article may be sent. The content syntax makes use of
   syntax defined in [RFC 2822].

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      header            =/ Complaints-To-header
                        = "Complaints-To" ":" SP Complaints-To-content
                        = address-list

   A Complaints-To-header MUST NOT be added to an article by any agent
   other than an injecting agent. Any Complaints-To-header present when
   an article arrives at an injecting agent MUST be removed. In
   particular if, for some exceptional reason (8.2.2), an article gets
   injected twice, the Complaints-To-header will always relate to the
   second injection.

   The specified mailbox is for sending complaints concerning the
   behaviour of the poster of the article; it SHOULD NOT be used for
   matters concerning propagation, protocol problems, etc. which should
   be addressed to "usenet@" or "news@" the path-identity which was
   prepended to the Path-header by the injecting agent, in accordance
   with section 5.6.2.  In the absence of this header, complaints
   concerning a poster's behaviour MAY be addressed to "abuse@" that
   path-identity (although section 5.6.2 provides no obligation for that
   address to be mailable at an injecting agent that is not provided for
   the use of the general public).

6.21.  MIME headers

6.21.1.  Syntax

   The following headers may be used within articles conforming to this

        MIME-Version:                [RFC 2045]
        Content-Type:                [RFC 2045],[RFC 2046]
        Content-Transfer-Encoding:   [RFC 2045]
        Content-ID:                  [RFC 2045]
        Content-Description:         [RFC 2045]
        Content-Disposition:         [RFC 2183]
        Content-Location:            [RFC 2557]
        Content-Language:            [RFC 3282]
        Content-MD5:                 [RFC 1864]

   The RFCs listed are deemed to be incorporated into this standard to
   the extent necessary to facilitate their usage within Netnews,
   subject to curtailment of that usage as described in the following
   sections. Moreover, extensions to those standards registered in
   accordance with [RFC 2048] are also available for use within Netnews,
   as indeed is any other header in the Content-* series which has a
   sensible interpretation within Netnews.

   Insofar as the syntax for these headers, as given in those RFCs does
   not specify precisely where whitespace and comments may occur
   (whether in the form of WSP, FWS or CFWS), the usage defined in this
   standard, and failing that in [RFC 2822], and failing that in [RFC
   822] MUST be followed. In particular, there MUST NOT be any WSP

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   between a header-name and the following colon and there MUST be a SP
   following that colon.

6.21.2.  Content-Type

   If the contents of an article is something other than plain text in
   the US-ASCII charset (these being the default assumptions), an
   appropriate Content-Type-header MUST be included.

   Reading agents SHOULD NOT, unless explicitly configured otherwise,
   act automatically on Application types which could change the state
   of that agent (e.g. by writing or modifying files), except in the
   case of those prescribed for use in control messages ( and

   The Content-Type "message/partial" MAY be used to split a long news
   article into several smaller ones. However, breaking long texts into
   several parts is usually unnecessary, since modern transport agents
   should have no difficulty in handling articles of arbitrary length,
   although it may be useful to break long binaries.

   IF the Content-Type "message/partial" is used, then the "id"
   parameter SHOULD be in the form of a unique message identifier (but
   different from that in the Message-ID-header of any of the parts).
   The second and subsequent parts SHOULD contain References-headers
   referring to all the previous parts, thus enabling reading agents
   with threading capabilities to present them in the correct order.
   Reading agents MAY then provide a facility to recombine the parts
   into a single article (but this standard does not require them to do

   The Content-Type "message/rfc822" should be used for the
   encapsulation (whether as part of another news article or, more
   usually, as part of an email message) of complete news articles which
   have already been posted to Netnews and which are for the information
   of the recipient, and do not constitute a request to repost them
   (refer to for the now obsolete "message/news" formerly
   intended for this purpose).

6.21.3.  Content-Transfer-Encoding

   "Content-Transfer-Encoding: 7bit" is sufficient for article bodies
   (or parts of multiparts) written in pure US-ASCII (or most other
   material representable in 7 bits).  Posting agents SHOULD specify
   "Content-Transfer-Encoding: 8bit" for all other cases except where
   the content is (or might be) "8bit-unsafe", or where some protocol
   explicitly disallows it. They MAY use "8bit" encoding even when
   "7bit" encoding would have sufficed.

   Content is "8bit-unsafe" if it contains octets equivalent to the US-
   ASCII characters CR or LF (other than in the combination CRLF) or
   NUL. This is often the case with application types (though in many
   cases application types are intended to be human readable, in which
   case they will usually be 8bit-safe). It also arises with certain

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   charsets (as indicated in the Content-Type-header), particularly in
   the case of 16-bit charsets such as UTF-16 ([UNICODE 3.2] or [ISO/IEC

   Examples of protocols REQUIRING particular Content-Transfer-Encodings
   include the Content-Type "application/pgp-signature" [RFC 3156], and
   the Content-Type "message/partial" which itself MUST use "Content-
   Transfer-Encoding: 7bit" (though the encapsulated complete message
   may itself use encoding "quoted-printable" or "base64", but that
   information is only conveyed along with the first of the partial

   Encoding "binary" MUST NOT be used (except in cooperating subnets
   with alternative transport arrangements) because this standard does
   not mandate a transport mechanism that could support it.

   Injecting and relaying agents MUST NOT change the encoding of
   articles passed to them. Gateways SHOULD NOT change the encoding
   unless absolutely necessary.

6.21.4.  Character Sets

[This section to be removed]

6.21.5.  Content Disposition

[This section to be removed]

6.21.6.  Definition of some new Content-Types

   This standard defines (or redefines) several new Content-Types, which
   require to be registered with IANA as provided for in [RFC 2048].
   For "application/news-groupinfo" see, for "application/news-
   checkgroups" see, and for "application/news-transmission" see
   the following section.  Application/news-transmission

   The Content-Type "application/news-transmission" is intended for the
   encapsulation of complete news articles where the intention is that
   the recipient should then inject them into Netnews. This Application
   type provides one of the methods for mailing articles to moderators
   (see 8.2.2) and it is also the preferred method when sending to an
   email-to-news gateway (see 8.8.2).

        NOTE: The benefit of such encapsulation is that it removes
        possible conflict between news and email headers and it provides
        a convenient way of "tunnelling" a news article through a
        transport medium that does not support 8bit characters.

   The MIME content type definition of "application/news-transmission"

   MIME type name:           application

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   MIME subtype name:        news-transmission
   Required parameters:      none
   Optional parameters:      usage=moderate
   Encoding considerations:  A transfer-encoding (such as Quoted-
                             Printable or Base64) different from that of
                             the article transmitted MAY be supplied
                             (perhaps en route) to ensure correct
                             transmission over some 7bit transport
   Security considerations:  A news article may be a "control message",
                             which could have effects on the recipient
                             host's system beyond just storage of the
                             article. However, such control messages
                             also occur in normal news flow, so most
                             hosts will already be suitably defended
                             against undesired effects.
   Published specification:  [USEFOR]
   Body part:                A complete article or proto-article, ready
                             for injection into Netnews, or a batch of
                             such articles.

        NOTE: It is likely that the recipient of an "application/news-
        transmission" will be a specialized gateway (e.g. a moderator's
        submission address) able to accept articles with only one of the
        three usage parameters "moderate", "inject" and "relay", hence
        the reason why they are optional, being redundant in most
        situations. Nevertheless, they MAY be used to signify the
        originator's intention with regard to the transmission, so
        removing any possible doubt.

   When the parameter "relay" is used, or implied, the body part MAY be
   a batch of articles to be transmitted together, in which case the
   following syntax MUST be used.

      batch             = 1*( batch-header article )
      batch-header      = "#!" SP rnews SP article-size CRLF
      rnews             = %x72.6E.65.77.73 ; case sensitive "rnews"
      article-size      = 1*DIGIT

   Thus a batch is a sequence of articles, each prefixed by a header
   line that includes its size. The article-size is a decimal count of
   the octets in the article, counting each CRLF as one octet regardless
   of how it is actually represented.

        NOTE: Despite the similarity of this format to an executable
        UNIX script, it is EXTREMELY unwise to feed such a batch into a
        command interpreter in anticipation of it running a command
        named "rnews"; the security implications of so doing would be

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                          News Article Format                  June 2003  Message/news obsoleted

   The Content-Type "message/news", as previously registered with IANA,
   is hereby declared obsolete. It was never widely implemented, and its
   default treatment as "application/octet-stream" by agents that did
   not recognize it was counter productive. The Content-Type
   "message/rfc822" SHOULD be used in its place, as already described

6.22.  Obsolete Headers

   Persons writing new agents SHOULD ignore any former meanings of the
   following headers:


7.  Control Messages

   The following sections document the control messages.  "Message" is
   used herein as a synonym for "article" unless context indicates

   The Newsgroups-header of each control message SHOULD include the
   newsgroup-name(s) for the group(s) affected (i.e. groups to be
   created, modified or removed, or containing articles to be canceled).
   This is to ensure that the message propagates to all sites which
   receive (or would receive) that group(s). It MAY include other
   newsgroup-names so as to improve propagation (but this practice may
   cause the control message to propagate also to places where it is
   unwanted, or even cause it not to propagate where it should, so it
   should not be used without good reason).

   The descriptions below set out REQUIREMENTS to be followed by sites
   that receive control messages and choose to honour them. However,
   nothing in these descriptions should be taken as overriding the right
   of any such site, in accordance with its local policy, to deny any
   particular control message, or to refer it to an administrator for
   approval (either as a class or on a case-by-case basis).

   Relaying Agents MUST propagate even control messages that they do not

   In the following sections, each type of control message is defined
   syntactically by defining its verb, its arguments, and possibly its

7.1.  Digital Signature of Headers

   It is most desirable that group control messages (7.2) in particular
   be authenticated by incorporating them within some digital signature
   scheme that encompasses other headers closely associated with them

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   (including at least the Approved-, Message-ID- and Date-headers). At
   the time of writing, this is usually done by means of a protocol
   known as "PGPverify" ([PGPVERIFY]), and continued usage of this is
   encouraged at least as an interim measure.

   However, PGPverify is not considered suitable for standardization in
   its present form, for various technical reasons. It is therefore
   expected that an early extension to this standard will provide a
   robust and general purpose digital authentication mechanism with
   applicability to all situations requiring protection against
   malicious use of, or interference with, headers.  That extension
   would also address other Netnews security issues.

7.2.  Group Control Messages

   "Group control messages" are the sub-class of control messages that
   request some update to the configuration of the groups known to a
   serving agent, namely "newgroup".  "rmgroup", "mvgroup" and
   "checkgroups", plus any others created by extensions to this

   All of the group control messages MUST have an Approved-header
   (6.14) which, in those hierarchies where appropriate administrative
   agencies exist (see 1.1), identifies the appropriate person or entity
   as authorized by those agencies.  The authorized person or entity
   SHOULD adhere to the conventions and restrictions on the format of
   newsgroup-names established for those hierarchies (see 5.5).

7.2.1.  The 'newgroup' Control Message

      control-message     =/ Newgroup-message
      Newgroup-message    = "newgroup" Newgroup-arguments
      Newgroup-arguments  = CFWS newsgroup-name [ CFWS newgroup-flag ]
      newgroup-flag       = "moderated"

   The "newgroup" control message requests that the specified group be
   created or changed. If the request is honoured, or if the group
   already exists on the serving agent, and if the newgroup-flag
   "moderated" is present, then the group MUST be marked as moderated,
   and vice versa. "Moderated" is the only such flag defined by this
   standard; other flags MAY be defined for use in cooperating subnets,
   but newgroup messages containing them MUST NOT be acted on outside of
   those subnets.

        NOTE: Specifically, some alternative flags such as "y" and "m",
        which are sent and recognized by some current software, are NOT
        part of this standard.  Moreover, some existing implementations
        treat any flag other than "moderated" as indicating an
        unmoderated newsgroup. Both of these usages are contrary to this
        standard and control messages with such non-standard flags
        should be ignored.

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   The message body comprises or includes an "application/news-
   groupinfo" ( part containing machine- and human-readable
   information about the group.

   The newgroup command is also used to update the newsgroups-line or
   the moderation status of a group.  The Body of the 'newgroup' Control Message

   The body of the newgroup message contains the following subparts,
   preferably in the order shown:

   1. An "application/news-groupinfo" part ( containing the name
      and newsgroups-line of the group(s). This part MUST be present.

   2. Other parts containing useful information about the background of
      the newgroup message (typically of type "text/plain").

   3. Parts containing initial articles for the newsgroup. See section for details.

   In the event that there is only the single (i.e. application/news-
   groupinfo) subpart present, it will suffice to include a "Content-
   Type:  application/news-groupinfo" amongst the headers of the control
   message.  Otherwise, a "Content-Type: multipart/mixed" header will be
   needed, and each separate part will then need its own Content-Type-
   header.  Application/news-groupinfo

   The "application/news-groupinfo" body part contains brief information
   about a newsgroup, i.e. the group's name, it's newsgroup-description
   and the moderation-flag.

        NOTE: The presence of the newsgroups-tag "For your newsgroups
        file:" is intended to make the whole newgroup message compatible
        with current practice as described in [Son-of-1036].

   The MIME content type definition of "application/news-groupinfo" is:

   MIME type name:           application
   MIME subtype name:        news-groupinfo
   Required parameters:      none
   Disposition:              by default, inline
   Encoding considerations:  "7bit" or "8bit" is sufficient and MUST be
                             used to maintain compatibility.
   Security considerations:  this type MUST NOT be used except as part
                             of a control message for the creation or
                             modification of a Netnews newsgroup
   Published specification:  [USEFOR]

   The content of the "application/news-groupinfo" body part is defined

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      groupinfo-body      = [ newsgroups-tag CRLF ]
                               newsgroups-line CRLF
      newsgroups-tag      = %x46.6F.72 SP %x79.6F.75.72 SP
                               %x6E. SP
                               ; case sensitive
                               ; "For your newsgroups file:"
      newsgroups-line     = newsgroup-name
                               [ 1*HTAB newsgroup-description ]
                               [ 1*WSP moderation-flag ]
                          = utext *( *WSP utext )
      moderation-flag     = %x28.4D.6F.
                               ; case sensitive "(Moderated)"

   The newsgroup-description MUST NOT contain any occurrence of the
   string "(Moderated)" within it.

   The "application/news-groupinfo" is used in conjunction with the
   "newgroup" (7.2.1) and "mvgroup" (7.2.3) control messages.  The
   newsgroup-name in the newsgroups-line MUST agree with the newsgroup-
   name in the "newgroup" or "mvgroup" control message.  The Content-
   Type "application/news-groupinfo" MUST NOT be used except as a part
   of such control messages.  Although optional, the newsgroups-tag
   SHOULD be included until such time as this standard has been widely
   adopted, to ensure compatibility with present practice.

   Moderated newsgroups MUST be marked by appending the case sensitive
   text " (Moderated)" at the end. It is NOT recommended that the
   moderator's email address be included in the newsgroup-description as
   has sometimes been done.

        NOTE: There is no provision for the use of charsets other than
        US-ASCII within a newsgroup-description. Such a facility may be
        provided in a future extension to this standard.
[That may seem harsh, but if we make any such provision now, it will
make life more complicated and restrict our freedom when it comes to the
proposed I18N extension. Therefore I resisted the temptation to include
any charset parameter with this Content-Type. Note that this also
applies to the checkgroups message further on.]  Initial Articles

   Some subparts of a "newgroup" or "mvgroup" control message MAY
   contain an initial set of articles to be posted to the affected
   newsgroup(s) as soon as it has been created or modified. These parts
   are identified by having the Content-Type "application/news-
   transmission", possibly with the parameter "usage=inject".  The body
   of each such part should be a complete proto-article, ready for
   posting. This feature is intended for the posting of charters,
   initial FAQs and the like to the newly formed group(s).

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   The Newsgroups-header of the proto-article MUST include the
   newsgroup-name of the newly created or modified group. It MAY include
   other newsgroup-names. If the proto-article includes a Message-ID-
   header, the message identifier in it MUST be different from that of
   any existing article and from that of the control message as a whole.
   Alternatively such a message identifier MAY be derived by the
   injecting agent when the proto-article is posted. The proto-article
   SHOULD include the header "Distribution: local".

   The proto-article SHOULD be injected at the serving agent that
   processes the control message AFTER the newsgroup in question has
   been created or modified.  It MUST NOT be injected if the newsgroup
   is not, in fact, created (for whatever reason). It MUST NOT be
   submitted to any relaying agent for transmission beyond the serving
   agent(s) upon which the newsgroup creation has just been effected (in
   other words, it is to be treated as having a "Distribution:  local"
   header, whether such a header is actually present or not).

        NOTE: It is not precluded that the proto-article is itself a
        control message or other type of special article, to be
        activated only upon creation of the new newsgroup. However,
        except as might arise from that possibility, any
        "application/news-transmission" within some nested "multipart/*"
        structure within the proto-article is not to be activated.  Example

   A "newgroup" with its charter:

      From: "example.all Administrator" <admin@noc.example>
      Newsgroups: example.admin.info,example.admin.announce
      Date: 27 Feb 2002 12:50:22 +0200
      Subject: cmsg newgroup example.admin.info moderated
      Approved: admin@noc.example
      Control: newgroup example.admin.info moderated
      Message-ID: <ng-example.admin.info-20020227@noc.example>
      MIME-Version: 1.0
      Content-Type: multipart/mixed; boundary="nxtprt"
      Content-Transfer-Encoding: 8bit

      This is a MIME control message.
      Content-Type: application/news-groupinfo

      For your newsgroups file:
      example.admin.info      About the example.* groups (Moderated)

      Content-Type: application/news-transmission

      Newsgroups: example.admin.info
      From: "example.all Administrator" <admin@noc.example>
      Subject: Charter for example.admin.info
      Message-ID: <charter-example.admin.info-20020227@noc.example>

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      Distribution: local
      Content-Type: text/plain; charset=us-ascii
      Content-Transfer-Encoding: 7bit

      The group example.admin.info contains regularly posted
      information on the example.* hierarchy.


7.2.2.  The 'rmgroup' Control Message

      control-message     =/ Rmgroup-message
      Rmgroup-message     = "rmgroup" Rmgroup-arguments
      Rmgroup-arguments   = CFWS newsgroup-name

   The "rmgroup" control message requests that the specified group be
   removed from the list of valid groups. The Content-Type of the body
   is unspecified; it MAY contain anything, usually an explanatory text.

        NOTE: It is entirely proper for a serving agent to retain the
        group until all the articles in it have expired, provided that
        it ceases to accept new articles.  Example

   Plain "rmgroup":

      From: "example.all Administrator" <admin@noc.example>
      Newsgroups: example.admin.obsolete, example.admin.announce
      Date: 4 Apr 2002 22:04 -0900 (PST)
      Subject: cmsg rmgroup example.admin.obsolete
      Message-ID: <rm-example.admin.obsolete-20020404@noc.example>
      Approved: admin@noc.example
      Control: rmgroup example.admin.obsolete

      The group example.admin.obsolete is obsolete. Please remove it
      from your system.

7.2.3.  The 'mvgroup' Control Message

      control-message   =/ Mvgroup-message
      Mvgroup-message   = "mvgroup" Mvgroup-arguments
      Mvgroup-arguments = CFWS newsgroup-name CFWS newsgroup-name
                             [ CFWS newgroup-flag ]

   The "mvgroup" control message requests that the group specified by
   the first (old-)newsgroup-name be moved to that specified by the
   second (new-)newsgroup-name. Thus it is broadly equivalent to a
   "newgroup" control message for the second group followed by a
   "rmgroup" control message for the first group.

   The message body contains an "application/news-groupinfo" part
   ( containing machine- and human-readable information about
   the new group, and possibly other subparts as for a "newgroup"

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   control message. The information conveyed in the "application/news-
   groupinfo" body part, notably its newsgroups-line (, is
   applied to the new group.

   When this message is received, the new group is created (if it does
   not exist already) as for a "newgroup" control message, and MUST in
   any case be made moderated if a newgroup-flag "moderated" is present,
   and vice versa. At the same time, arrangements SHOULD be made to
   remove the old group (as with a "rmgroup" control message), but only
   after a suitable overlap period to allow the network to adjust to the
   new arrangement.

   At the same time as a serving agent acts upon this message, all
   injecting agents associated with that serving agent SHOULD inhibit
   the posting of new articles to the old group (preferably with some
   indication to the poster that the new group should have been used).
   Relaying agents, however, MUST continue to propagate such articles
   during the overlap period.

        NOTE: It is to be expected that different serving agents will
        act on this message at different points of time, users of the
        old group will have to become accustomed to the new arrangement,
        and followups to already established threads will likely
        continue under the old group. Therefore, there needs to be an
        overlap period during which articles may continue to be accepted
        by relaying and serving agents in either group. This standard
        does not specify any standard period of overlap (though it would
        be expected to be expressed in days rather than in months). The
        inhibition of injection of new articles to the old group may
        seem draconian, but it is the surest way to prevent the
        changeover from dragging on indefinitely.

   Since the "mvgroup" control message is newly introduced in this
   standard and may not be widely implemented initially, it SHOULD be
   followed shortly afterwards by a corresponding "newgroup" control
   message; and again, after a reasonable overlap period, it MUST be
   followed by a "rmgroup" control message for the old group.

   In order to facilitate a smooth changeover, serving agents MAY
   arrange to service requests for access to the old group by providing
   access to the new group, which would then contain, or appear to
   contain, all articles posted to either group (including, ideally, the
   pre-changeover articles from the old one). Nevertheless, if this
   feature is implemented, the articles themselves, as supplied to
   reading agents, MUST NOT be altered in any way (and, in particular,
   their Newsgroups-headers MUST contain exactly those newsgroups
   present when they were injected). On the other hand, the Xref-header
   MAY contain entries for either group (or even both).

        NOTE: Some serving agents that use an "active" file permit an
        entry of the form "oldgroup xxx yyy =newgroup", which enables
        any articles arriving for oldgroup to be diverted to newgroup,
        thus providing a simple implementation of this feature. However,
        it is known that not all current serving agents will find

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        implementation so easy (especially in the short term) which is
        why it is not mandated by this standard. Nevertheless, its
        eventual implementation in all serving agents is to be
        considered highly desirable.

        On the other hand, it is recognized that this feature would
        likely not be implementable if the new group was already in
        existence with existing articles in it. This situation should
        not normally arise except when there is already some confusion
        as to which groups are, or are not, supposed to exist in that
        hierarchy. Note that the "mvgroup" control message is not really
        intended to be used for merging two existing groups.  Example

      From: "example.all Administrator" <admin@noc.example>
      Newsgroups: example.oldgroup,example.newgroup,example.admin.announce
      Date: 30 Apr 2002 22:04 -0500 (EST)
      Subject: cmsg mvgroup example.oldgroup example.newgroup moderated
      Message-ID: <mvgroup-example.oldgroup-20020430@noc.example>
      Approved: admin@noc.example
      Control: mvgroup example.oldgroup example.newgroup moderated
      MIME-Version: 1.0
      Content-Type: multipart/mixed; boundary=nxt

      Content-Type: application/news-groupinfo

      For your newsgroups file:
      example.newgroup        The new replacement group (Moderated)


      The moderated group example.oldgroup is replaced by
      example.newgroup. Please update your configuration, and please,
      if possible, arrange to file articles arriving for
      example.oldgroup as if they were in example.newgroup.


7.2.4.  The 'checkgroups' Control Message

   The "checkgroups" control message contains a list of all the valid
   groups in a complete hierarchy.

      control-message     =/ Checkgroup-message
      Checkgroup-message  = "checkgroups" Checkgroup-arguments
      Checkgroup-arguments= [ chkscope ] [ chksernr ]
      chkscope            = 1*( CFWS ["!"] newsgroup-name )
      chksernr            = CFWS "#" 1*DIGIT

   A "checkgroups" message applies to any (sub-)hierarchy with a prefix
   listed in the chkscope parameter, provided that the rightmost
   matching newsgroup-name in the list is not immediately preceded by a

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   "!".  If no chkscope parameter is given, it applies to all
   hierarchies for which group statements appear in the message.

        NOTE: Some existing software does not support the "chkscope"
        parameter.  Thus a "checkgroups" message SHOULD also contain the
        groups of other subhierarchies the sender is not responsible
        for. "New" software MUST ignore groups which do not fall within
        the chkscope parameter of the "checkgroups" message.

   The chksernr parameter is a serial number, which can be any positive
   integer (e.g. just numbered or the date in YYYYMMDD).  It SHOULD
   increase by an arbitrary value with every change to the group list
   and MUST NOT ever decrease.

        NOTE: This was added to circumvent security problems in
        situations where the Date-header cannot be authenticated.


      Control: checkgroups de !de.alt #248

   which includes the whole of the 'de.*' hierarchy, with the exception
   of its 'de.alt.*' sub-hierarchy.

   The body of the message has the Content-Type "application/news-
   checkgroups".  It asserts that the newsgroups it lists are the only
   newsgroups in the specified hierarchies.

        NOTE: The checkgroups message is intended to synchronize the
        list of newsgroups stored by a serving agent, and their
        newsgroup-descriptions, with the lists stored by other serving
        agents throughout the network. However, it might be inadvisable
        for the serving agent actually to create or delete any
        newsgroups without first obtaining the approval of its
        administrators for such proposed actions.  Application/news-checkgroups

   The "application/news-checkgroups" body part contains a complete list
   of all the newsgroups in a hierarchy, their newsgroup-descriptions
   and their moderation status.

   The MIME content type definition of "application/news-checkgroups"

   MIME type name:           application
   MIME subtype name:        news-checkgroups
   Required parameters:      none
   Disposition:              by default, inline
   Encoding considerations:  "7bit" or "8bit" is sufficient and MUST be
                             used to maintain compatibility.
   Security considerations:  this type MUST NOT be used except as part
                             of a checkgroups control message

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   The content of the "application/news-checkgroups" body part is
   defined as:

      checkgroups-body    = *( valid-group CRLF )
      valid-group         = newsgroups-line ; see

   The "application/news-checkgroups" content type is used in
   conjunction with the "checkgroups" control message (7.2.4).

        NOTE: The possibility of removing a complete hierarchy by means
        of an "invalidation" line beginning with a '!' is no longer
        provided by this standard. The intent of the feature was widely
        misunderstood and it was misused more often than it was used
        correctly. The same effect, if required, can now be obtained by
        the use of an appropriate chkscope argument in conjunction with
        an empty checkgroups-body.

7.3.  Cancel

   The cancel message requests that a target article be "canceled" i.e.
   be withdrawn from circulation or access.

      control-message     =/ Cancel-message
      Cancel-message      = "cancel" Cancel-arguments
      Cancel-arguments    = CFWS msg-id [CFWS]

   The argument identifies the article to be cancelled by its message
   identifier.  The body SHOULD contain an indication of why the
   cancellation was requested. The cancel message SHOULD be posted to
   the same newsgroup, with the same distribution, as the article it is
   attempting to cancel.

   A serving agent that elects to honour a cancel message SHOULD make
   the article unavailable for relaying or serving (perhaps by deleting
   it completely). If the target article is unavailable, and the
   acceptability of the cancel message cannot be established without it,
   activation of the cancel message SHOULD be delayed until the target
   article has been seen.  See also sections 8.3 and 8.4.

        NOTE: It is expected that the security extension envisaged in
        section 7.1 will make more detailed provisions for establishing
        whether honouring a particular cancel message is in order. In
        particular, it is likely that there will be provision for the
        digital signature of 3rd party cancels (i.e. those issued other
        than by the sender, the moderator, or the injector).

        NOTE: A cancel submitted by the poster for an article in a
        moderated group will be forwarded to the moderator of that
        group, and it is up to that moderator to act upon it (8.7).

        NOTE: The former requirement [RFC 1036] that the From and/or
        Sender-headers of the cancel message should match those of the
        original article has been removed from this standard, since it

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        only encouraged cancel issuers to conceal their true identity,
        and it was not usually checked or enforced by canceling
        software.  Therefore, both the From and/or Sender-headers and
        any Approved-header should now relate to the entity responsible
        for issuing the cancel message.

7.4.  Ihave, sendme

   The "ihave" and "sendme" control messages implement a crude batched
   predecessor of the NNTP [NNTP] protocol. They are largely obsolete on
   the Internet, but still see use in conjunction with some transport
   protocols such as UUCP, especially for backup feeds that normally are
   active only when a primary feed path has failed. There is no
   requirement for relaying agents that do not support such transport
   protocols to implement them.

        NOTE: The ihave and sendme messages defined here have ABSOLUTELY
        NOTHING TO DO WITH NNTP, despite similarities of terminology.

   The two messages share the same syntax:

      control-message     =/ Ihave-message
      Ihave-message       = "ihave" Ihave-arguments
      Ihave-arguments     = relayer-name
      control-message     =/ Sendme-message
      Sendme-message      = "sendme" Sendme-arguments
      Sendme-arguments    = Ihave-arguments
      relayer-name        = path-identity  ; see 5.6.1
      ihave-body          = *( msg-id CRLF )
      sendme-body         = ihave-body

   The body of the message consists of a list of msg-ids, one per line.
   [RFC 1036] also permitted the list of msg-ids to appear in the Ihave-
   or Sendme-arguments with the syntax
      Ihave-arguments     = [FWS] *( msg-id FWS ) [relayer-name]
   but this form SHOULD NOT now be used, though relaying agents MAY
   recognize and process it for backward compatibility.

   The ihave message states that the named relaying agent has received
   articles with the specified message identifiers, which may be of
   interest to the relaying agents receiving the ihave message.  The
   sendme message requests that the agent receiving it send the articles
   having the specified message identifiers to the named relaying agent.

   These control messages are normally sent essentially as point-to-
   point messages, by using newsgroup-names in the Newsgroups-header of
   the form "to."  followed by one (or possibly more) components in the
   form of a relayer-name (see section 5.5.1 which forbids "to" as the
   first component of a newsgroup-name). The control message SHOULD then
   be delivered ONLY to the relaying agent(s) identified by that
   relayer-name, and any relaying agent receiving such a message which
   includes its own relayer-name MUST NOT propagate it further. Each
   pair of relaying agent(s) sending and receiving these messages MUST
   be immediate neighbors, exchanging news directly with each other.

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   Each relaying agent advertises its new arrivals to the other using
   ihave messages, and each uses sendme messages to request the articles
   it lacks.

   To reduce overhead, ihave and sendme messages SHOULD be sent
   relatively infrequently and SHOULD contain reasonable numbers of
   message IDs. If ihave and sendme are being used to implement a backup
   feed, it may be desirable to insert a delay between reception of an
   ihave and generation of a sendme, so that a slightly slow primary
   feed will not cause large numbers of articles to be requested
   unnecessarily via sendme.

7.5.  Obsolete control messages.

   The following control messages are declared obsolete by this


8.  Duties of Various Agents

   The following section sets out the duties of various agents involved
   in the creation, relaying and serving of Usenet articles. Insofar as
   these duties are described as sequences of steps to be followed, it
   should be understood that it is the effect of these sequences that is
   important, and implementations may use any method that gives rise to
   that same effect.

   In this section, the word "trusted", as applied to the source of some
   article, means that an agent processing that article has verified, by
   some means, the identity of that source (which may be another agent
   or a poster).

        NOTE: In many implementations, a single agent may perform
        various combinations of the injecting, relaying and serving
        functions. Its duties are then the union of the various duties

8.1.  General principles to be followed

   There are two important principles that news implementors (and
   administrators) need to keep in mind. The first is the well-known
   Internet Robustness Principle:

        Be liberal in what you accept, and conservative in what you

   However, in the case of news there is an even more important
   principle, derived from a much older code of practice, the
   Hippocratic Oath (we may thus call this the Hippocratic Principle):

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        First, do no harm.

   It is VITAL to realize that decisions which might be merely
   suboptimal in a smaller context can become devastating mistakes when
   amplified by the actions of thousands of hosts within a few minutes.

   In the case of gateways, the primary corollary to this is:

        Cause no loops.

8.2.  Duties of an Injecting Agent

   An Injecting Agent is responsible for taking a proto-article from a
   posting agent and either forwarding it to a moderator or injecting it
   into the relaying system for access by readers.

   As such, an injecting agent is considered responsible for ensuring
   that any article it injects conforms with the rules of this standard.
   It is also expected to bear some responsibility towards the rest of
   the network for the behaviour of its posters (and provision is
   therefore made for it to be easily contactable by email).

8.2.1.  Proto-articles

   A proto-article is one that has been created by a posting agent and
   has not yet been injected into the news system by an injecting agent.
   It SHOULD NOT be propagated in that form to other than injecting
   agents. A proto-article has the same format as a normal article
   except that some of the following mandatory headers MAY be omitted:
   Message-Id-header, Date-header, Path-header (and even From-header if
   the particular injecting agent can derive that information from other
   sources). These headers MUST NOT contain invalid values; they MUST
   either be correct or not present at all.

   A proto-article SHOULD NOT contain the '%' path-delimiter in any
   Path-header, except in the rare cases where an article gets injected
   twice. It MAY contain path-identities with other path-delimiters in
   the pre-injection portion of the Path-header (5.6.3).

8.2.2.  Procedure to be followed by Injecting Agents

   A injecting agent receives proto-articles from posting and followup
   agents. It verifies them, adds headers where required and then either
   forwards them to a moderator or injects them by passing them to
   serving or relaying agents.

   If an injecting agent receives an otherwise valid article that has
   already been injected it SHOULD either act as if it is a relaying
   agent or else pass the article on to a relaying agent completely
   unaltered. Exceptionally, it MAY reinject the article, perhaps as a
   part of some complex gatewaying process (in which case it will add a
   second '%' path-delimiter to the Path-header).  It MUST NOT forward
   an already injected article to a moderator.

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   An injecting agent processes articles as follows:

   1. It MUST remove any Injector-Info- or Complaints-To-header already
      present (though it might be useful to copy them to suitable X-
      headers). It SHOULD likewise remove any NNTP-Posting-Host or other
      undocumented tracing header.

   2. It SHOULD verify that the article is from a trusted source.
      However, it MAY allow articles in which headers contain "forged"
      email addresses, that is, addresses which are not valid for the
      known and trusted source, especially if they end in ".invalid".

   3. It MUST reject any article whose Date-header is more than 24 hours
      into the past or into the future (cf. 5.1).

   4. It MUST reject any article that does not have the correct
      mandatory headers for a proto-article (5 and 8.2.1) present, or
      which contains any header that does not have syntactically legal
      contents.  It SHOULD reject any article which contains any header
      deprecated for Netnews (4.2.1).

   5. If the article is rejected (for reasons given above, or for other
      formatting errors or matters of site policy) the posting agent
      SHOULD be informed (such as via an NNTP 44x response code) that
      posting has failed and the article MUST NOT then be processed

   6. The Message-ID and Date-headers (and their contents) MUST be added
      when not already present.

   7. A Path-header with a tail-entry (5.6.3) MUST be correctly added if
      not already present (except that it SHOULD NOT be added if the
      article is to be forwarded to a moderator).

   8. The path-identity of the injecting agent with a '%' path-delimiter
      (5.6.2) MUST be prepended to the Path-header; moreover, that
      path-identity MUST be an FQDN mailable address (5.6.2).

   9. An Injector-Info-header (6.19) SHOULD be added, identifying the
      trusted source of the article, and a suitable Complaints-To-header
      (6.20) MAY be added (except that these two headers MUST NOT be
      added if the article is to be forwarded to a moderator).

   10.The injecting agent MUST NOT alter the body of the article in any
      way. It MAY add other headers not already provided by the poster,
      but SHOULD NOT alter, delete, or reorder any existing header, with
      the specific exception of "tracing" headers such as Injector-Info
      and Complaints-To, which are to be removed as already mentioned.

   11.If the Newsgroups-header contains no moderated groups, or if it
      contains an Approved-header, the injecting agent forwards the
      article to one or more relaying or serving agents.

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   12.Otherwise, when the Newsgroups-header contains one or more
      moderated groups and the article does NOT contain an Approved-
      header, the injecting agent MUST forward it to the moderator of
      the first (leftmost) moderated group listed in the Newsgroups-
      header via email. There are two possibilities for doing this:

      (a)  The complete article is encapsulated (headers and all) within
           the email, preferably using the Content-Type
           "application/news-transmission" ( with any usage
           parameter set to "moderate". Moreover, there SHOULD NOT be
           more than one encapsulated article within the one email.
           This method has the advantage of removing any possible
           conflict between Netnews and Email headers, or of changes to
           those headers during transport through email.

      (b)  The article is sent as an email as it stands, with the
           addition of such extra headers (e.g. a To-header) as are
           necessary for an email.

      Although both of these methods have seen use in the past, the
      preponderance of current usage on Usenet has been for method (b)
      and many moderators are ill-prepared to deal with method (a).
      Therefore, method (a) SHOULD NOT be used until such time as the
      majority of moderators are able to accept it.

   13.This standard does not prescribe how the email address of the
      moderator is to be determined, that being a matter of policy to be
      arranged by the agency responsible for the oversight of each
      hierarchy. Nevertheless, there do exist various agents worldwide
      which provide the service of forwarding to moderators, and the
      address to use with them is obtained as follows:

      (a)  Each '.' in the newsgroup-name is replaced with a '-'.

      (b)  The result of these operations is used as the local-part of
           the mailbox of the agent. For example, articles intended for
           "news.announce.important" would be emailed to "news-

8.3.  Duties of a Relaying Agent

   A Relaying Agent accepts injected articles from injecting and other
   relaying agents and passes them on to relaying or serving agents
   according to mutually agreed policy. Relaying agents SHOULD accept
   articles ONLY from trusted agents.

   A relaying agent processes articles as follows:

   1. It MUST verify the leftmost entry in the Path-header and then
      prepend its own path-identity with a '/' path-delimiter, and
      possibly also the verified path-identity of its source with a '?'
      path-delimiter (5.6.2).

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   2. It MUST reject any article whose Date-header is stale (see 5.1).

   3. It MUST reject any article that does not have the correct
      mandatory headers (section 5) present with legal contents.

   4. It SHOULD reject any article whose optional headers (section 6) do
      not have legal contents.

   5. It SHOULD reject any article that has already been sent to it (a
      database of message identifiers of recent messages is usually kept
      and matched against).

   6. It SHOULD reject any article that matches an already received
      cancel message (or an equivalent Supersedes-header) issued by its
      poster or by some other trusted entity.

   7. It MAY reject any article without an Approved-header posted to
      newsgroups known to be moderated (this practice is strongly
      recommended, but the information necessary to do it may not be
      available to all agents).

   8. It then passes articles which match mutually agreed criteria on to
      neighbouring relaying and serving agents. However, it SHOULD NOT
      forward articles to sites whose path-identity is already in the

        NOTE: It is usual for relaying and serving agents to restrict
        the Newsgroups, Distributions, age and size of articles that
        they wish to receive.

   If the article is rejected as being invalid, unwanted or unacceptable
   due to site policy, the agent that passed the article to the relaying
   agent SHOULD be informed (such as via an NNTP 43x response code) that
   relaying failed. In order to prevent a large number of error messages
   being sent to one location, relaying agents MUST NOT inform any other
   external entity that an article was not relayed UNLESS that external
   entity has explicitly requested that it be informed of such errors.

        NOTE: In order to prevent overloading, relaying agents should
        not routinely query an external entity (such as a DNS-server) in
        order to verify an article (though a local cache of the required
        information might usefully be consulted).

   Relaying agents MUST NOT alter, delete or rearrange any part of an
   article expect for headers designated as variant (

8.4.  Duties of a Serving Agent

   A Serving Agent takes an article from a relaying or injecting agent
   and files it in a "news database". It also provides an interface for
   reading agents to access the news database. This database is normally
   indexed by newsgroup with articles in each newsgroup identified by an
   article-locater (usually in the form of a decimal number - see 6.16).

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        NOTE: Since control messages are often of interest, but should
        not be displayed as normal articles in regular newsgroups, it is
        common for serving agents to make them available in a pseudo-
        newsgroup named "control" or in a pseudo-newsgroup in a sub-
        hierarchy under "control." (e.g. "control.cancel").

   A serving agent processes articles as follows:

   1. It MUST verify the leftmost entry in the Path-header and then
      prepend its own path-identity with a '/' path-delimiter, and
      possibly also the verified path-identity of its source with a '?'
      path-delimiter (5.6.2).

   2. It MUST reject any article whose Date-header is stale (see 5.1).

   3. It MUST reject any article that does not have the correct
      mandatory headers (section 5) present, or which contains any
      header that does not have legal contents.

   4. It SHOULD reject any article that has already been sent to it (a
      database of message identifiers of recent messages is usually kept
      and matched against).

   5. It SHOULD reject any article that matches an already received
      cancel message (or an equivalent Supersedes-header) issued by its
      poster or by some other trusted entity.

   6. It MUST reject any article without an Approved-header posted to
      any moderated newsgroup which it is configured to receive, and it
      MAY reject such articles for any newsgroup it knows to be

   7. It MUST remove any Xref-header (6.16) from each article.  It then
      MAY (and usually will) generate a fresh Xref-header.

   8. Finally, it stores the article in its news database.

8.5.  Duties of a Posting Agent

   A Posting Agent is used to assist the poster in creating a valid
   proto-article and forwarding it to an injecting agent.

   Postings agents SHOULD ensure that proto-articles they create are
   valid news articles according to this standard and other applicable

   Posting agents meant for use by ordinary posters SHOULD reject any
   attempt to post an article which cancels or Supersedes another
   article of which the poster is not the author.

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8.6.  Duties of a Followup Agent

   A Followup Agent is a special case of a posting agent and as such is
   bound by all the posting agent's requirements. Followup agents MUST
   create valid followups and are subject to the following special
   requirements involving certain inheritable ( and other

   1. The Newsgroups-header (5.5) SHOULD be initialized from the
      precursor's Followup-To-header, if present, when preparing a
      followup; however posters MAY then change this before posting if
      they wish.

   2. The Subject-content (5.4) of the precursor MAY (and usually will)
      be prepended with the back-reference "Re: " (which is case
      sensitive), unless that precursor is itself a followup with "Re: "
      already present in its Subject-content; however posters MAY then
      change this before posting if they wish.

      Followup agents MUST NOT use any other string except "Re: " as a
      back-reference, and specifically NOT a translation of "Re: " into
      a local language, and they MUST NOT prepend a "Re: " if one is
      already present.
[The provision of back-references and their allowed forms are still
under discussion in the Usefor Working Group.
The matter of a "Re: " occurring within an encoded-word needs to be

        NOTE: "Re" is an abbreviation for the Latin "In re", meaning "in
        the matter of", and not an abbreviation of "Reference" as is
        sometimes erroneously supposed. Reading agents often take note
        of a single "Re: " at the beginning of a Subject-content (for
        example, in order to display a list of articles sorted by
        Subject). These restrictions ensure that reading agents have no
        need to recognize more than a single occurrence of "Re: ".

   3. The Distribution-header (6.6) SHOULD be initialized from the
      precursor's Distribution-header, if any; however posters MAY then
      change this before posting if they wish.

   4. If the precursor did not have a References-header (6.10), the
      followup's References-content MUST be formed by the message
      identifier of the precursor. A followup to an article which had a
      References-header MUST have a References-header containing the
      precursor's References-content (subject to trimming as described
      below) plus the precursor's message identifier appended to the end
      of the list (separated from it by CFWS).

      Followup agents MAY trim References-headers which have grown to
      excessive length, but the first and last message identifiers from
      the precursor MUST NOT be removed.

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   5. If the precursor contains a Mail-Copies-To-header (6.8), The
      actions to be taken, in accordance with the Mail-Copies-To-
      content, (and subject to manual override by the poster) are as

      "nobody" (or when the header is absent)
            The followup agent SHOULD NOT email a copy of the followup
            to the poster of the precursor.

            The followup agent SHOULD (if it has the necessary
            capability) email a copy of the followup, which MUST then be
            sent to the address(es) in the Reply-To-header, and in the
            absence of that to the address(es) in the From-header.

      a copy-addr
            The followup agent SHOULD likewise email a copy of the
            followup, which MUST then be sent to the copy-addr.

      When emailing a copy, the followup agent SHOULD also include a
      "Posted-And-Mailed: yes" header (6.9).

      Followup agents MUST NOT attempt to send email to any address
      ending in ".invalid".

8.7.  Duties of a Moderator

   A Moderator receives news articles by email, decides whether to
   accept them and, if so, either injects them into the news stream or
   forwards them to further moderators.

   Articles will be received by the moderator either encapsulated as an
   object of Content-Type application/news-transmission (or possibly
   encapsulated but without an explicit Content-Type-header), or else
   directly as an email already containing all the headers appropriate
   for a Netnews article (see 8.2.2).  Moderators SHOULD be prepared to
   accept articles in either format.

   A moderator processes an article, as submitted to any newsgroup that
   he moderates, as follows:

   1. He decides, on the basis of whatever moderation policy applies to
      his group, whether to accept or reject the article. He MAY do this
      manually, or else partially or wholly with the aid of appropriate
      software for whose operation he is then responsible.  If the
      article is a cancel nessage (7.3) issued by the poster of an
      earlier article, then he is expected to cancel that earlier
      article (in which case there is no more to be done).  He MAY
      modify the article if that is in accordance with the applicable
      moderation policy (and in particular he MAY remove redundant
      headers and add Comments and other informational headers).  He
      also needs to be aware if any change he makes to the article will
      invalidate some authentication check provided by the poster or by
      an earlier moderator.

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      If the article is rejected, then it normally fails for all the
      newsgroups for which it was intended. If it is accepted, the
      moderator proceeds with the following steps.

   2. If the Newsgroups-header contains further moderated newsgroups for
      which approval has not already been given, he adds an indication
      (identifying both himself and the name of the group) that he
      approves the article, and then forwards it to the moderator of the
      leftmost unapproved group (which, if this standard has been
      followed correctly, will generally be the next moderated group to
      the right of his own). There are two ways to do this:

      (a)  He emails it to the submission address of the next moderator
           (see section 8.2.2 for the proper method of doing this), or

      (b)  he rotates the newsgroup-names in the Newsgroups-header to
           the left so that the targeted group is the leftmost moderated
           group in that header, and injects it as below (thus causing
           the injecting agent to email it to the correct moderator).
           However, he MUST first ensure that the article contains no

        NOTE: This standard does not prescribe how a moderator's
        approval is to be indicated (though a future standard may do
        so).  Possible methods include adding an Approved header (or a
        similar but differently named header if method (b) is being
        used) listing all the approvals made so far, or adding a
        separate header for each individual approval (the header X-Auth
        is sometimes used for this purpose).  The approval may also be
        confirmed with some form of digital signature (7.1).

   3. If the Newsgroups-header contains no further unapproved moderated
      groups, he adds an Approved-header (6.14) identifying himself and,
      insofar as is possible, all the other moderators who have approved
      the article. He thus assumes responsibility for having ensured
      that the article was acceptable to the moderators of all the
      moderated groups involved.

   4. The Date-header SHOULD be retained, except that if it is stale
      (5.1) for reasons understood by the moderator (e.g. delays in the
      moderation process) he MAY substitute the current date (but must
      then take responsibility for any loops that ensue). The Message-
      ID-header SHOULD also be retained unless it is obviously non-
      compliant with this standard.

        NOTE: A message identifier created by a conforming posting or
        injecting agent, or even by a mail user agent conforming to [RFC
        2822], may reasonably be supposed to be conformant (and will, in
        any case, be caught by the injecting agent if it is not).

   5. Any variant headers ( MUST be removed, except that a
      Path-header MAY be truncated to only its pre-injection region
      (5.6.3).  Any Injector-Info-header (6.19) or Complaints-To-header
      (6.20) MUST be removed.

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   6. He then causes the article to be injected, having first observed
      all the duties of a posting agent.

        NOTE: This standard does not prescribe how the moderator or
        moderation policy for each newsgroup is established; rather it
        assumes that whatever agencies are responsible for the relevant
        network or hierarchy (1.1) will have made appropriate
        arrangements in that regard.

8.8.  Duties of a Gateway

   A Gateway transforms an article into the native message format of
   another medium, or translates the messages of another medium into
   news articles. Encapsulation of a news article into a message of MIME
   type application/news-transmission, or the subsequent undoing of that
   encapsulation, is not gatewaying, since it involves no transformation
   of the article.

   There are two basic types of gateway, the Outgoing Gateway that
   transforms a news article into a different type of message, and the
   Incoming Gateway that transforms a message from another medium into a
   news article and injects it into a news system. These are handled
   separately below.

   The primary dictat for a gateway is:

        Above all, prevent loops.

   Transformation of an article into another medium stands a very high
   chance of discarding or interfering with the protection inherent in
   the news system against duplicate articles. The most common problem
   caused by gateways is "spews," gateway loops that cause previously
   posted articles to be reinjected repeatedly into Usenet. To prevent
   this, a gateway MUST take precautions against loops, as detailed

   If bidirectional gatewaying (both an incoming and an outgoing
   gateway) is being set up between Netnews and some other medium, the
   incoming and outgoing gateways SHOULD be coordinated to avoid
   reinjection of gated articles. Circular gatewaying (gatewaying a
   message into another medium and then back into Netnews) SHOULD NOT be
   done; encapsulation of the article SHOULD be used instead where this
   is necessary.

   A second general principal of gatewaying is that the transformations
   applied to the message SHOULD be as minimal as possible while still
   accomplishing the gatewaying. Every change made by a gateway
   potentially breaks a property of one of the media or loses
   information, and therefore only those transformations made necessary
   by the differences between the media should be applied.

   It is worth noting that safe bidirectional gatewaying between a
   mailing list and a newsgroup is far easier if the newsgroup is
   moderated. Posts to the moderated group and submissions to the

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   mailing list can then go through a single point that does the
   necessary gatewaying and then sends the message out to both the
   newsgroup and the mailing list at the same time, eliminating most of
   the possibility of loops. Bidirectional gatewaying between a mailing
   list and an unmoderated newsgroup, in contrast, is difficult to do
   correctly and is far more fragile.

   Newsgroups intended to be bidirectionally gated to a mailing list
   SHOULD therefore be moderated where possible, even if the moderator
   is a simple gateway and injecting agent that correctly handles
   crossposting to other moderated groups and otherwise passes all

8.8.1.  Duties of an Outgoing Gateway

   From the perspective of Netnews, an outgoing gateway is just a
   special type of reading agent. The exact nature of what the outgoing
   gateway will need to do to articles depends on the medium to which
   the articles are being gated. The operation of the outgoing gateway
   is only subject to additional constraints in the presence of one or
   more corresponding incoming gateways back from that medium to
   Netnews, since this opens the possibility of loops.

   In general, the following practices are recommended for all outgoing
   gateways, regardless of whether there is known to be a related
   incoming gateway, both as a precautionary measure and as a guideline
   to quality of implementation.

   1. The message identifier of the news article should be preserved if
      at all possible, preferably as or within the corresponding unique
      identifier of the other medium, but if not at least as a comment
      in the message. This helps greatly with preventing loops.

   2. The Date of the news article should also be preserved if possible,
      for similar reasons.

   3. The message should be tagged in some way so as to prevent its
      reinjection into Netnews. This may be impossible to do without
      knowledge of potential incoming gateways, but it is better to try
      to provide some indication even if not successful; at the least, a
      human-readable indication that the article should not be gated
      back to Netnews can help locate a human problem.

   4. Netnews control messages should not be gated to another medium
      unless they would somehow be meaningful in that medium.

8.8.2.  Duties of an Incoming Gateway

   The incoming gateway has the serious responsibility of ensuring that
   all of the requirements of this standard are met by the articles that
   it forms. In addition to its special duties as a gateway, it bears
   all of the duties and responsibilities of an injecting agent as well,
   and additionally has the same responsibility of a relaying agent to
   reject articles that it has already gatewayed.

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   An incoming gateway MUST NOT gate the same message twice. It may not
   be possible to ensure this in the face of mangling or modification of
   the message, but at the very least a gateway, when given a copy of a
   message it has already gated identical except for trace headers (like
   Received in Email or Path in Netnews) MUST NOT gate the message
   again.  An incoming gateway SHOULD take precautions against having
   this rule bypassed by modifications of the message that can be

   News articles prepared by gateways MUST be legal news articles. In
   particular, they MUST include all of the mandatory headers, MUST
   fully conform to the restrictions on said headers, and SHOULD exclude
   any deprecated headers (4.2.1).  This often requires that a gateway
   function not only as a relaying agent, but also partly as a posting
   agent, aiding in the synthesis of a conforming article from non-
   conforming input.

   Incoming gateways MUST NOT pass control messages (articles containing
   a Control- or Supersedes-header) without removing or renaming that
   header. Gateways MAY, however, generate their own cancel messages,
   under the general allowance for injecting agents to cancel their own
   messages (7.3).  If a gateway receives a message that it can
   determine is a valid equivalent of a cancel message in the medium it
   is gatewaying, it SHOULD discard that message without gatewaying it,
   generate a corresponding cancel message of its own, and inject that
   cancel message.

   Incoming gateways MUST NOT inject control messages other than
   cancels.  Encapsulation SHOULD be used instead of gatewaying, when
   direct posting is not possible or desirable.

        NOTE: It is not unheard of for mail-to-news gateways to be used
        to post control messages, but encapsulation should be used for
        these cases instead. Gateways by their very nature are
        particularly prone to loops. Spews of normal articles are bad
        enough; spews of control messages with special significance to
        the news system, possibly resulting in high processing load or
        even email sent for every message received, are catastrophic. It
        is far preferable to construct a system specifically for posting
        control messages that can do appropriate consistency checks and
        authentication of the originator of the message.

   If there is a message identifier that fills a role similar to that of
   the Message-ID-header in news, it SHOULD be used in the formation of
   the message identifier of the news article, perhaps with
   transformations required to meet the uniqueness requirement of
   Netnews and with the removal of any comments so as to comply with the
   syntax in section 5.3. Such transformations SHOULD be designed so
   that two messages with the same identifier generate the same

        NOTE: Message identifiers play a central role in the prevention
        of duplicates, and their correct use by gateways will do much to
        prevent loops. Netnews does, however, require that message

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        identifiers be unique, and therefore message identifiers from
        other media may not be suitable for use without modification. A
        balance must be struck by the gateway between preserving
        information used to prevent loops and generating unique message

   Exceptionally, if there are multiple incoming gateways for a
   particular set of messages, each to a different newsgroup(s), each
   one SHOULD generate a message identifier unique to that gateway. Each
   incoming gateway nonetheless MUST ensure that it does not gate the
   same message twice.

        NOTE: Consider the example of two gateways of a given mailing
        list into the world-wide Usenet newsgroups, both of which
        preserve the email message identifier. Each newsgroup may then
        receive a portion of the messages (different sites seeing
        different portions).  In these cases, where there is no one
        "official" gateway, some other method of generating message
        identifiers has to be used to avoid collisions. It would
        obviously be preferable for there to be only one gateway which
        crossposts, but this may not be possible to coordinate.

   If no date information is available, the gateway MAY supply a Date-
   header with the gateway's current date. If only partial information
   is available (e.g.  date but not time), this SHOULD be fleshed out to
   a full Date-header by adding default values rather than discarding
   this information. Only in very exceptional circumstances should Date
   information be discarded, as it plays an important role in preventing
   reinjection of old messages.

   An incoming gateway MUST add a Sender-header to the news article it
   forms containing the mailbox of the administrator of the gateway.
   Problems with the gateway may be reported to this mailbox. The
   display-name portion of this mailbox SHOULD indicate that the entity
   responsible for injection of the message is a gateway. If the
   original message already had a Sender-header, it SHOULD be renamed so
   that its contents can be preserved.

8.8.3.  Example

   To illustrate the type of precautions that should be taken against
   loops, here is an example of the measures taken by one particular
   combination of mail-to-news and news-to-mail gateways at Stanford
   University designed to handle bidirectional gatewaying between
   mailing lists and unmoderated groups.

   1. The news-to-mail gateway preserves the message identifier of the
      news article in the generated email message. The mail-to-news
      gateway likewise preserves the email message identifier provided
      that it is syntactically valid for Netnews.  This allows the news
      system's built-in suppression of duplicates to serve as the first
      line of defense against loops.

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   2. The news-to-mail gateway adds an X-Gateway-header to all messages
      it generates. The mail-to-news gateway discards any incoming
      messages containing this header. This is robust against mailing
      list managers that replace the message identifier, and against any
      number of email hops, provided that the other message headers are

   3. The mail-to-news gateway inserts the host name from which it
      received the email message in the pre-injection region of the Path
      (5.6.3).  The news-to-mail gateway refuses to gateway any message
      that contains the list server name in the pre-injection region of
      its Path-header. This is robust against any amount of munging of
      the message headers by the mailing list, provided that the email
      only goes through one hop.

   4. The mail-to-news gateway is designed never to generate bounces to
      the envelope sender. Instead, articles that are rejected by the
      news server (for reasons not warranting silent discarding of the
      message) result in a bounce message sent to an errors address
      known not to forward to any mailing lists, so that they can be
      handled by the news administrators.

   These precautions have proven effective in practice at preventing
   loops for this particular application (bidirectional gatewaying
   between mailing lists and locally distributed newsgroups where both
   gateways can be designed together). General gatewaying to world-wide
   newsgroups poses additional difficulties; one must be very wary of
   strange configurations, such as a newsgroup gated to a mailing list
   which is in turn gated to a different newsgroup.

9.  Security and Related Considerations

   There is no security. Don't fool yourself. Usenet is a prime example
   of an Internet Adhocratic-Anarchy; that is, an environment in which
   trust forms the basis of all agreements.  It works.

9.1.  Leakage

   Articles which are intended to have restricted distribution are
   dependent on the goodwill of every site receiving them.  The
   "Archive: no" header (6.12) is available as a signal to automated
   archivers not to file an article, but that cannot be guaranteed.

   The Distribution-header makes provision for articles which should not
   be propagated beyond a cooperating subnet. The key security word here
   is "cooperating". When a machine is not configured properly, it may
   become uncooperative and tend to distribute all articles.

   The flooding algorithm is extremely good at finding any path by which
   articles can leave a subnet with supposedly restrictive boundaries,
   and substantial administrative effort is required to avoid this.
   Organizations wishing to control such leakage are strongly advised to
   designate a small number of official gateways to handle all news
   exchange with the outside world (however, making such gateways too

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   restrictive can also encourage the setting up of unofficial paths
   which can be exceedingly hard to track down).

   The sendme control message (7.4), insofar as it is still used, can be
   used to request articles with a given message identifier, even one
   that is not supposed to be supplied to the requestor.

9.2.  Attacks

9.2.1.  Denial of Service

   The proper functioning of individual newsgroups can be disrupted by
   the massive posting of "noise" articles, by the repeated posting of
   identical or near identical articles, by posting followups unrelated
   to their precursors, or which quote their precursors in full with the
   addition of minimal extra material (especially if this process is
   iterated), and by crossposting to, or setting followups to, totally
   unrelated newsgroups.

   Many have argued that "spam", massively multiposted (and to a lesser
   extent massively crossposted) articles, usually for advertising
   purposes, also constitutes a DoS attack in its own regard.  This may
   be so.

   Such articles intended to deny service, or other articles of an
   inflammatory nature, may also have their From or Reply-To addresses
   set to valid but incorrect email addresses, thus causing large
   volumes of email to descend on the true owners of those addresses.

   Similar effects could be caused by any email header which could cause
   every reading agent receiving it to take some externally visible
   action.  For example, the Disposition-Notification-To-header defined
   in [RFC 2298] could cause huge numbers of acknowledgements to be
   emailed to an unsuspecting third party (for which reason [RFC 2298]
   declares that that header SHOULD NOT be used in Netnews).

   It is a violation of this standard for a poster to use as his address
   a mailbox which he is not entitled to use.  Even addresses with an
   invalid local-part but a valid domain can cause disruption to the
   administrators of such domains.  Posters who wish to remain anonymous
   or to prevent automated harvesting of their addresses, but who do not
   care to take the additional precautions of using more sophisticated
   anonymity measures, should avoid that violation by the use of
   addresses ending in the ".invalid" top-level-domain (see 5.2).

   A malicious poster may also prevent his article being seen at a
   particular site by preloading that site into the Path-header (5.6.1)
   and may thus prevent the true owner of a forged From or Reply-To
   address from ever seeing it.

   A malicious complainer may submit a modified copy of an article (e.g.
   with an altered Injector-Info-header) to the administrator of an
   injecting agent in an attempt to discredit the author of that article
   and even to have his posting privileges removed. Administrators

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   should therefore obtain a genuine copy of the article from their own
   serving agent before taking such precipitate action.

   Administrative agencies with responsibility for establishing policies
   in particular hierarchies can and should set bounds upon the
   behaviour that is considered acceptable within those hierarchies (for
   example by promulgating charters for individual newsgroups, and other
   codes of conduct).

   Whilst this standard places an onus upon injecting agents to bear
   responsibility for the misdemeanours of their posters (which includes
   non-adherence to established policies of the relevant hierarchies as
   provided in section 8.2), and to provide assistance to the rest of
   the network by making proper use of the Injector-Info- (6.19) and
   Complaints-To- (6.20) headers, it makes no provision for enforcement,
   which may in consequence be patchy. Nevertheless, injecting sites
   which persistently fail to honour their responsibilities or to comply
   with generally accepted standards of behaviour are likely to find
   themselves blacklisted, with their articles refused propagation and
   even subject to cancellation, and other relaying sites would be well
   advised to withdraw peering arrangements from them.

9.2.2.  Compromise of System Integrity

   The posting of unauthorized (as determined by the policies of the
   relevant hierarchy) control messages can cause unwanted newsgroups to
   be created, or wanted ones removed, from serving agents.
   Administrators of such agents SHOULD therefore take steps to verify
   the authenticity of such control messages, either by manual
   inspection (particularly of the Approved-header) or by checking any
   digital signatures that may be provided (see 7.1).  In addition, they
   SHOULD periodically compare the newsgroups carried against any
   regularly issued checkgroups messages, or against lists maintained by
   trusted servers and accessed by out-of-band protocols such as FTP or

   Malicious cancel messages (7.3) can cause valid articles to be
   removed from serving agents. Administrators of such agents SHOULD
   therefore take steps to verify that they originated from the
   (apparent) poster, the injector or the moderator of the article, or
   that in other cases they came from a place that is trusted to work
   within established policies and customs. Such steps SHOULD include
   the checking of any digital signatures, or other security devices,
   that may be provided (see 7.1).  Articles containing Supersedes-
   headers (6.15) are effectively cancel messages, and SHOULD be subject
   to the same checks.  Currently, many sites choose to ignore all
   cancel messages on account of the difficulty of conducting such

   Improperly configured serving agents can allow articles posted to
   moderated groups onto the net without first being approved by the
   moderator. Injecting agents SHOULD verify that moderated articles
   were received from one of the entities given in their Approved-
   headers and/or check any digital signatures that may be provided (see

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   The filename parameter of the Archive-header (6.12) can be used to
   attempt to store archived articles in inappropriate locations.
   Archiving sites should be suspicious of absolute filename parameters,
   as opposed to those relative to some location of the archiver's

   There may be weaknesses in particular implementations that are
   subject to malicious exploitation. In particular, it has not been
   unknown for complete shell scripts to be included within Control-
   headers. Implementors need to be aware of this.

   Reading agents should be chary of acting automatically upon MIME
   objects with an "application" Content-Type that could change the
   state of that agent, except in contexts where such applications are
   specifically expected (see 6.21).  Even the Content-Type "text/html"
   could have unexpected side effects on account of embedded objects,
   especially embedded executable code or URLs that invoke non-news
   protocols such as HTTP [RFC 2616].  It is therefore generally
   recommended that reading agents do not enable the execution of such
   code (since it is extremely unlikely to have a valid application
   within Netnews) and that they only honour URLs referring to other
   parts of the same article.

   Non-printable characters embedded in article bodies may have
   surprising effects on printers or terminals, notably by reconfiguring
   them in undesirable ways which may become apparent only after the
   reading agent has terminated.

9.3.  Liability

   There is a presumption that a poster who sends an article to Usenet
   intends it to be stored on a multitude of serving agents, and has
   therefore given permission for it to be copied to that extent.
   Nevertheless, Usenet is not exempt from the Copyright laws, and it
   should not be assumed that permission has been given for the article
   to be copied outside of Usenet, nor for its permanent archiving
   contrary to any Archive-header that may be present.

   Posters also need to be aware that they are responsible if they
   breach Copyright, Libel, Harassment or other restrictions relating to
   material that they post, and that they may possibly find themselves
   liable for such breaches in jurisdictions far from their own. Serving
   agents may also be liable in some jurisdictions, especially if the
   breach has been explicitly drawn to their attention.

   Users who are concerned about such matters should seek advice from
   competent legal authorities.

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10.  IANA Considerations

   IANA is requested to register the following media types, described
   elsewhere in this standard for use with the Content-Type-header, in
   the IETF tree in accordance with the procedures set out in [RFC

      application/news-transmission  (
      application/news-groupinfo     (
      application/news-checkgroups   (

   IANA is also requested to change the status of the following media
   type to "OBSOLETE".

      message/news                   (

        NOTE: "Application/news-transmission" is an update, with
        clarification and additional optional parameters, to an existing
        registration. "Message/rfc822" should now be used in place of
        the obsoleted "message/news".

11.  References

   [ANSI X3.4] "American National Standard for Information Systems -
        Coded Character Sets - 7-Bit American National Standard Code for
        Information Interchange (7-Bit ASCII)", ANSI X3.4, 1986.

   [ISO 3166] "Codes for the representation of names of countries and
        their subdivisions -- Part 1: Country codes", ISO 3166, 1997.

   [ISO/IEC 10646] "International Standard - Information technology -
        Universal Multiple-Octet Coded Character Set (UCS) - Part 1:
        Architecture and Basic Multilingual Plane", ISO/IEC 10646-
        1:2000, 2000.

   [KLYNE] G. Klyne and J. Mogul, "Registration procedures for message
        header fields", draft-klyne-msghdr-registry-06.txt.

   [NNTP] S. Barber, "Network News Transport Protocol", draft-ietf-

   [PGPVERIFY] David Lawrence,

   [RFC 1034] P. Mockapetris, "Domain Names - Concepts and Facilities",
        RFC 1034, November 1987.

   [RFC 1036] M. Horton and R. Adams, "Standard for Interchange of
        USENET Messages", RFC 1036, December 1987.

   [RFC 1864] J. Myers and M. Rose, "The Content-MD5 Header Field", RFC
        1864, October 1995.

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                          News Article Format                  June 2003

   [RFC 2045] N. Freed and N. Borenstein, "Multipurpose Internet Mail
        Extensions (MIME) Part One: Format of Internet Message Bodies",
        RFC 2045, November 1996.

   [RFC 2046] N. Freed and N. Borenstein, "Multipurpose Internet Mail
        Extensions (MIME) Part Two: Media Types", RFC 2046, November

   [RFC 2047] K. Moore, "MIME (Multipurpose Internet Mail Extensions)
        Part Three: Message Header Extensions for Non-ASCII Text", RFC
        2047, November 1996.

   [RFC 2048] N. Freed, J. Klensin, and J. Postel, "Multipurpose
        Internet Mail Extensions (MIME) Part Four: Registration
        Procedures", RFC 2048, November 1996.

   [RFC 2119] S. Bradner, "Key words for use in RFCs to Indicate
        Requirement Levels", RFC 2119, March 1997.

   [RFC 2142] D. Crocker, "Mailbox Names for Common Services, Roles and
        Functions", RFC 2142, May 1997.

   [RFC 2156] S. Kille, "MIXER (Mime Internet X.400 Enhanced Relay):
        Mapping between X.400 and RFC 822/MIME", RFC 2156, January 1998.

   [RFC 2183] R. Troost, S. Dorner, and K.Moore, "Communicating
        Presentation Information in Internet Messages: The Content-
        Disposition Header Field", RFC 2183, August 1997.

   [RFC 2231] N. Freed and K. Moore, "MIME Parameter Value and Encoded
        Word Extensions: Character Sets, Languages, and Continuations",
        RFC 2231, November 1997.

   [RFC 2234] D. Crocker and P. Overell, "Augmented BNF for Syntax
        Specifications: ABNF", RFC 2234, November 1997.

   [RFC 2279] F. Yergeau, "UTF-8, a transformation format of ISO 10646",
        RFC 2279, January 1998.

   [RFC 2279bis] F. Yergeau, "UTF-8, a transformation format of ISO
        10646", draft-yergeau-rfc2279bis-00.txt, April 2002.

   [RFC 2298] R. Fajman, "An Extensible Message Format for Message
        Disposition Notifications", RFC 2298, March 1998.

   [RFC 2373] R. Hinden and S. Deering, "IP Version 6 Addressing
        Architecture", RFC 2373, July 1998.

   [RFC 2557] J. Palme, A. Hopmann, and N. Shelness, "MIME Encapsulation
        of Aggregate Documents, such as HTML (MHTML)", RFC 2557, March

   [RFC 2606] D. Eastlake and A. Panitz, "Reserved Top Level DNS Names",
        RFC 2606, June 1999.

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   [RFC 2616] R. Fielding, J. Gettys, J. Mogul, H. Frystyk, L. Masinter,
        P. Leach, and T. Berners-Lee, "Hypertext Transfer Protocol --
        HTTP/1.1", RFC 2616, June 1999.

   [RFC 2822] P. Resnick, "Internet Message Format", RFC 2822, April

   [RFC 2978] N. Freed and J. Postel, "IANA Charset Registration
        Procedures", RFC 2978, October 2000.

   [RFC 3066] H. Alvestrand, "Tags for the Identification of Languages",
        RFC 3066, January 2001.

   [RFC 3156] M. Elkins, D. Del Torto, R. Levien, and T. Roessler, "MIME
        Security with OpenPGP", RFC 3156, August 2001.

   [RFC 3282] H. Alvestrand, "Content Language Headers", RFC 3282, May

   [RFC 822] D. Crocker, "Standard for the Format of ARPA Internet Text
        Messages.", STD 11, RFC 822, August 1982.

   [RFC 850] Mark R. Horton, "Standard for interchange of Usenet
        messages", RFC 850, June 1983.

   [RFC 976] Mark R. Horton, "UUCP mail interchange format standard",
        RFC 976, February 1986.

   [Son-of-1036] Henry Spencer, "News article format and transmission",
        <ftp://ftp.zoo.toronto.edu/pub/news.txt.Z>, June 1994.

   [UNICODE 3.0] The Unicode Consortium, "The Unicode Standard - Version
        3.0", Addison-Wesley, 2000.

   [UNICODE 3.1] The Unicode Consortium, "The Unicode Standard - Version
        3.1, being an amendment to [UNICODE 3.0]", Unicode Standard
        Annex #27 <http://www.unicode.org/unicode/reports/tr27>, 2001.

   [UNICODE 3.2] The Unicode Consortium, "The Unicode Standard - Version
        3.2, being an amendment to [UNICODE 3.1]", Unicode Standard
        Annex #28 <http://www.unicode.org/unicode/reports/tr28>, 2002.

   [USEAGE] Draft in preparation.

   [USEFOR] This Standard.

12.  Acknowledgements

   The editor wishes to thank the following members of the IETF Usenet
   Format Working Group who made significant contributions to this
   endeavour (however, inclusion in this list does not imply that a
   person approves of everything contained herein).

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   Per Abrahamsen                Brian Kelly
   Peter Alfredsen               Evan Kirshenbaum
   Russ Allbery                  Brad Knowles
   Greg Andruk                   Kent Landfield
   Ralph Babel                   David C. Lawrence
   Stan Barber                   Bruce Lilly
   Dave Barr                     Simon Lyall
   Ian Bell                      Todd Michel McComb
   G. James Berigan              Denis McKeon
   Terje Bless                   Seymour J. Metz
   Seth Breidbart                John Moreno
   Buddha Buck                   Chris Newman
   Forrest J. Cavalier III       Dirk Nimmich
   Evan Champion                 Paul Overell
   Maurizio Codogno              Jacob Palme
   Don Croyle                    Brian Palmer
   Matt Curtin                   Pete Resnick
   Bill Davidsen                 Jon Ribbens
   Ian Davis                     Dan Ritter
   Jean-Marc Desperrier          Thomas Roessler
   Martin J. Duerst              Doug Royer
   Claus Andre Faerber           Frederic Senis
   Clive D.W. Feather            Erland Sommarskog
   David Formosa                 Henry Spencer
   Marty Fouts                   John Stanley
   Benjamin Franz                Brad Templeton
   Andrew Gierth                 Florian Weimer
   Jonathan Grobe                Curt Welch
   Thomas Gschwind               Curtis Whalen
   Kai Henningsen                Leonid Yegoshin
   Lars Magne Ingebrigtsen       Jamie Zawinski

13.  Contact Address


        Charles. H. Lindsey
        5 Clerewood Avenue
        Heald Green
        Cheshire SK8 3JU
        United Kingdom
        Phone: +44 161 436 6131
        Email: chl@clw.cs.man.ac.uk


Working group chairs

        Andrew Gierth <andrew@erlenstar.demon.co.uk>
        Pete Resnick <presnick@qualcomm.com>

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   Comments on this draft should preferably be sent to the mailing list
   of the Usenet Format Working Group at


   This draft expires six months after the date of publication (see Page
   1) (i.e. in Dec 2003).

Appendix A.1 - A-News Article Format

   The obsolete "A News" article format consisted of exactly five lines
   of header information, followed by the body. For example:

      Fri Nov 19 16:14:55 1982
      Usenet Etiquette - Please Read

   The first line consisted of an "A" followed by an article ID
   (analogous to a message ID and used for similar purposes).  The
   second line was the list of newsgroups. The third line was the path.
   The fourth was the date, in the format above (all fields fixed
   width), resembling an Internet date but not quite the same. The fifth
   was the subject.

   This format is documented for archeological purposes only.  Articles
   MUST NOT be generated in this format.

Appendix A.2 - Early B-News Article Format

   The obsolete pseudo-Internet article format, used briefly during the
   transition between the A News format and the modern format, followed
   the general outline of a MAIL message but with some non-standard
   headers. For example:

      From: cbosgd!mhuxj!mhuxt!eagle!jerry (Jerry Schwarz)
      Newsgroups: news.misc
      Title: Usenet Etiquette -- Please Read
      Article-I.D.: eagle.642
      Posted: Fri Nov 19 16:14:55 1982
      Received: Fri Nov 19 16:59:30 1982
      Expires: Mon Jan 1 00:00:00 1990


   The From-header contained the information now found in the Path-
   header, plus possibly the full name now typically found in the From-
   header. The Title-header contained what is now the Subject-content.

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   The Posted-header contained what is now the Date-content. The
   Article-I.D.-header contained an article ID, analogous to a message
   ID and used for similar purposes. The Newsgroups- and Expires-headers
   were approximately as now. The Received-header contained the date
   when the latest relaying agent to process the article first saw it.
   All dates were in the above format, with all fields fixed width,
   resembling an Internet date but not quite the same.

   This format is documented for archeological purposes only.  Articles
   MUST NOT be generated in this format.

Appendix A.3 - Obsolete Headers

   Early versions of news software following the modern format sometimes
   generated headers like the following:

      Relay-Version: version B 2.10 2/13/83; site cbosgd.UUCP
      Posting-Version: version B 2.10 2/13/83; site eagle.UUCP
      Date-Received: Friday, 19-Nov-82 16:59:30 EST

   Relay-Version contained version information about the relaying agent
   that last processed the article. Posting-Version contained version
   information about the posting agent that posted the article. Date-
   Received contained the date when the last relaying agent to process
   the article first saw it (in a slightly nonstandard format).

   In addition, this present standard obsoletes certain headers defined
   in [Son-of-1036] (see 6.22):

      Also-Control: cancel <9urrt98y53@site.example>
      See-Also: <i4g587y@site1.example> <kgb2231+ee@site2.example>
      Article-Names: comp.foo:charter
      Article-Updates: <i4g587y@site1.example>

   Also-Control indicated a control message that was also intended to be
   filed as a normal article. See-Also listed related articles, but
   without the specific relationship with followups that pertains to the
   References-header.  Article-Names indicated some special significance
   of that article in relation to the indicated newsgroup. Article-
   Updates indicated that an earlier article was updated, without at the
   same time being superseded.

   These headers are documented for archeological purposes only.
   Articles containing these headers MUST NOT be generated.

Appendix A.4 - Obsolete Control Messages

   This present standard obsoletes certain control messages defined in
   [RFC 1036] (see 7.5), all of which had the effect of requesting a
   description of a relaying or serving agent's software, or its peering
   arrangements with neighbouring sites, to be emailed to the article's
   reply address. Whilst of some utility when Usenet was much smaller
   than it is now, they had become no more than a tool for the malicious
   sending of mailbombs. Moreover, many organizations now consider

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   information about their internal connectivity to be confidential.


   "Version" requested details of the transport software in use at a
   site.  "Sendsys" requested the full list of newsgroups taken, and the
   peering arrangements. "Who gets" was similar, but restricted to a
   named newsgroup.  "Senduuname" resembled "sendsys" but restricted to
   the list of peers connected by UUCP.

   Historically, a checkgroups body consisting of one or two lines, the
   first of the form "-n newsgroup", caused check-groups to apply to
   only that single newsgroup.

   Historically, an article posted to a newsgroup whose name had exactly
   three components of which the third was "ctl" signified that article
   was to be taken as a control message.  The Subject-header specified
   the actions, in the same way the Control-header does now.

   These forms are documented for archeological purposes only; they MUST
   NO LONGER be used.

Appendix B - Collected Syntax

Appendix B.1 - Characters, Atoms and Folding

   In the following syntactic rules, numbers in the left hand margin
   indicate rules taken from other documents, specifically:
     1 from  [RFC 2231];
     2 from  [RFC 2822] with the exception of those elements described
       therein as "obsolete";
     3 from  [RFC 2373];
     4 from  [RFC 2234];
     5 from  [RFC 2045].

   Where the number is followed by an asterisk ('*'), it indicates that
   the rule in question has been modified for the purposes of this

4  ALPHA                = %x41-5A /        ; A-Z
                          %x61-7A          ; a-z
2  CFWS                 = *([FWS] comment) ( ([FWS] comment) / FWS )
4  CR                   = %x0D             ; carriage return
4  CRLF                 = CR LF
4  DIGIT                = %x30-39          ; 0-9
4  DQUOTE               = %d34             ; quote mark
2  FWS                  = ([*WSP CRLF] 1*WSP); folding whitespace
4  HEXDIG               = DIGIT / "A" / "B" / "C" / "D" / "E" / "F"
4  HTAB                 = %x09             ; horizontal tab
4  LF                   = %x0A             ; line feed

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2  NO-WS-CTL            = %d1-8 /          ; US-ASCII control characters
                          %d11 /           ; which do not include the
                          %d12 /           ; carriage return, line feed,
                          %d14-31 /        ; and whitespace characters
4  SP                   = %x20             ; space
4  WSP                  = SP / HTAB        ; whitespace characters
2  atext                = ALPHA / DIGIT /
                          "!" / "#" /      ; Any character except
                          "$" / "%" /      ; controls, SP, and specials.
                          "&" / "'" /      ; Used for atoms
                          "*" / "+" /
                          "-" / "/" /
                          "=" / "?" /
                          "^" / "_" /
                          "`" / "{" /
                          "|" / "}" /
2  atom                 = [CFWS] 1*atext [CFWS]
2* ccontent             = ctext / quoted-pair / comment / encoded-word
   charset              = <registered character set name>
                                           ;  [RFC 2978]
2  comment              = "(" *([FWS] ccontent) [FWS] ")"
2  ctext                = NO-WS-CTL /      ; all of <text> except
                          %d33-39 /        ; SP, HTAB, "(", ")"
                          %d42-91 /        ; and "\"
1  encoded-word         = "=?" charset ["*" language] "?" encoding
                             "?" encoded-text "?="
2  dcontent             = dtext / quoted-pair
2  dot-atom             = [CFWS] dot-atom-text [CFWS]
2  dot-atom-text        = 1*atext *( "." 1*atext )
2  dtext                = NO-WS-CTL /      ; Non white space controls
                          %d33-90 /        ; The rest of the US-ASCII
                          %d94-126         ; characters not including
                                           ; "[", "]", or "
   extended-phrase      = ( [CFWS] encoded-word [CFWS] / word )
                             *( [CFWS] encoded-word [CFWS] / word  /
                                [CFWS] "." [CFWS] )
   language             = <registered language tag>
                                           ;  [RFC 3066]
2* phrase               = 1*( [CFWS] encoded-word [CFWS] / word ) /
2  qcontent             = qtext / quoted-pair
2  qtext                = NO-WS-CTL /      ; all of <text> except
                          %d33 /           ; SP, HTAB, "\" and DQUOTE
                          %d35-91 /
2  quoted-pair          = "\" text
2  quoted-string        = [CFWS] DQUOTE
                             *( [FWS] qcontent ) [FWS]
                             DQUOTE [CFWS]

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2  specials             = "(" / ")" /      ; Special characters used in
                          "<" / ">" /      ;  other parts of the syntax
                          "[" / "]" /
                          ":" / ";" /
                          "@" / "\" /
                          "," / "." /
2  text                 = %d1-9 /          ; all UTF-8 characters except
                          %d11-12 /        ; US-ASCII NUL, CR and LF
5  tspecials            = "(" / ")" / "<" / ">" / "@" /
                          "," / ";" / ":" / "\" / DQUOTE /
                          "/" / "[" / "]" / "?" / "="
2* unstructured         = 1*( [FWS] ( utext / encoded-word ) ) [FWS]
2  utext                = NO-WS-CTL /      ; Non white space controls
                          %d33-126         ; The rest of US-ASCII
2  word                 = atom / quoted-string

Appendix B.2 - Basic Forms

2  addr-spec            = local-part "@" domain
2  address              = mailbox / group
2  address-list         = address *( "," address )
2  angle-addr           = [CFWS] "<" addr-spec ">" [CFWS]
   article              = 1*( header CRLF ) separator body
1  attribute            = 1*attribute-char
1  attribute-char       = <any (US-ASCII) CHAR except SPACE, CTLs,
                             "*", "'", "%", or tspecials>
   body                 = *( *998text CRLF )
2  display-name         = phrase
2  date                 = day month year
2  date-time            = [ day-of-week "," ] date FWS time [CFWS]
2  day                  = [FWS] 1*2DIGIT
2  day-name             = "Mon" / "Tue" / "Wed" / "Thu" /
                          "Fri" / "Sat" / "Sun"
2  day-of-week          = [FWS] day-name
2  domain               = dot-atom / domain-literal
2  domain-literal       = [CFWS] "[" *([FWS] dcontent) [FWS] "]" [CFWS]
1  extended-initial-name
                        = attribute [initial-section] "*"
1  extended-initial-value
                        = [charset] "'" [language] "'"
1  extended-other-names = attribute other-section "*"
1* extended-other-value = *( "%" 2HEXDIG / attribute-char )
1* extended-parameter   = ( [CFWS] extended-initial-name [CFWS]
                             "=" extended-initial-value ) /
                          ( [CFWS] extended-other-names [CFWS]
                             "=" extended-other-values )
   extension-parameter  = <a parameter not defined by this standard>
2  group                = display-name ":" [ mailbox-list / CFWS ] ";"
   header-name          = 1*name-character *( "-" 1*name-character )
2  hour                 = 2DIGIT

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1  initial-section      = "*0"
2  local-part           = dot-atom / quoted-string
2  mailbox              = name-addr / addr-spec
2  mailbox-list         = mailbox *( "," mailbox )
2  minute               = 2DIGIT
2  month                = FWS month-name FWS
2  month-name           = "Jan" / "Feb" / "Mar" / "Apr" /
                          "May" / "Jun" / "Jul" / "Aug" /
                          "Sep" / "Oct" / "Nov" / "Dec"
2  name-addr            = [display-name] angle-addr
   name-character       = ALPHA / DIGIT
   other-header         = header-name ":" 1*SP other-content
   other-content        = <the content of a header defined by some
                             other standard>
   other-section        = "*" ("1" / "2" / "3" / "4" / "5" /
                              "6" / "7" / "8" / "9") *DIGIT
1  parameter            = regular-parameter / extended-parameter
1* regular-parameter    = [CFWS] regular-parameter-name [CFWS]
                             "=" value
1  regular-parameter-name
                        = attribute [section]
2  second               = 2DIGIT
1  section              = initial-section / other-section
   separator            = CRLF
2  time                 = time-of-day FWS zone
2  time-of-day          = hour ":" minute [ ":" second ]
5  token                = 1*<any (US-ASCII) CHAR except SP, CTLs,
                             or tspecials>
5  value                = [CFWS] token [CFWS] / quoted-string
   x-attribute          = "x-" attribute
2  year                 = 4*DIGIT
2* zone                 = (( "+" / "-" ) 4DIGIT) / "UT" / "GMT"

Appendix B.3 - Headers

Appendix B.3.1 - Header outlines

   header               = other-header /
                          Date-header /
                          From-header /
                          Message-ID-header /
                          Subject-header /
                          Newsgroups-header /
                          Path-header /
                          Reply-To-header /
                          Sender-header /
                          Organization-header /
                          Keywords-header /
                          Summary-header /
                          Distribution-header /
                          Followup-To-header /
                          Mail-Copies-To-header /
                          Posted-And-Mailed-header /
                          References-header /

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                          Expires-header /
                          Archive-header /
                          Control-header /
                          Approved-header /
                          Supersedes-header /
                          Xref-header /
                          Lines-header /
                          User-Agent-header /
                          Injector-Info-header /

   Approved-content     = From-content
   Approved-header      = "Approved" ":" SP Approved-content
                             *( ";" extension-parameter )
   Archive-content      = [CFWS] ("no" / "yes" ) [CFWS]
   Archive-header       = "Archive" ":" SP Archive-content
                             *( ";" ( Archive-parameter /
                                      extension-parameter ) )
   Archive-parameter    = <a parameter with attribute "filename"
                           and any value>
   Complaints-To-content= address-list
   Complaints-To-header = "Complaints-To" ":" SP Complaints-To-content
   Control-content      = [CFWS] control-message [CFWS]
   Control-header       = "Control" ":" SP Control-content
                             *( ";" extension-parameter )
   Date-content         = date-time
   Date-header          = "Date" ":" SP Date-content
   Distribution-content = distribution *( dist-delim distribution )
   Distribution-header  = "Distribution" ":" SP Distribution-content
                             *( ";" extension-parameter )
   Expires-content      = date-time
   Expires-header       = "Expires" ":" SP Expires-content
                             *( ";" extension-parameter )
   Followup-To-content  = Newsgroups-content /
                          [FWS] %x70.6F. [FWS]
                          ; which is a case-sensitive "poster"
   Followup-To-header   = "Followup-To" ":" SP Followup-To-content
                             *( ";" extension-parameter )
   From-content         = mailbox-list
   From-header          = "From" ":" SP From-content
   Injector-Info-content= [CFWS] path-identity [CFWS]
   Injector-Info-header = "Injector-Info" ":" SP Injector-Info-content
                             *( ";" ( Injector-Info-parameter /
                                      extension-parameter ) )
                        = posting-host-parameter /
                          posting-account-parameter /
                          posting-sender-parameter /
                          posting-logging-parameter /
   Keywords-content     = phrase *( "," phrase )
   Keywords-header      = "Keywords" ":" SP Keywords-content
   Lines-content        = [CFWS] 1*DIGIT [CFWS]

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   Lines-header         = "Lines" ":" SP Lines-content
                             *( ";" extension-parameter )
                        = copy-addr / [CFWS] ( "nobody" /
                                      "poster" ) [CFWS]
   Mail-Copies-To-header= "Mail-Copies-To" ":" SP Mail-Copies-To-content
   Message-ID-content   = [FWS] msg-id [FWS]
   Message-ID-header    = "Message-ID" ":" SP Message-ID-content
   Newsgroups-content   = [FWS] newsgroup-name
                             *( [FWS] ng-delim [FWS] newsgroup-name )
   Newsgroups-header    = "Newsgroups"  ":" SP Newsgroups-content
                                  *( ";" extension-parameter )
   Organization-content = unstructured
   Organization-header  = "Organization" ":" SP Organization-content
   Path-content         = [FWS] *( path-identity [FWS]
                                      path-delimiter [FWS]
                                 ) tail-entry [FWS]
   Path-header          = "Path" ":" SP Path-content
                             *( ";" extension-parameter )
                        = [CFWS] ( "yes" / "no" ) [CFWS]
                        = "Posted-And-Mailed" ":" SP
                             *( ";" extension-parameter )
   References-content   = [CFWS] msg-id *( CFWS msg-id ) [CFWS]
   References-header    = "References" ":" SP References-content
   Reply-To-content     = address-list
   Reply-To-header      = "Reply-To" ":" SP Reply-To-content
   Sender-content       = mailbox
   Sender-header        = "Sender" ":" SP Sender-content
   Subject-content      = [ [FWS] back-reference ] pure-subject
   Subject-header       = "Subject" ":" SP Subject-content
   Summary-content      = unstructured
   Summary-header       = "Summary" ":" SP Summary-content
   Supersedes-content   = [CFWS] msg-id [CFWS]
   Supersedes-header    = "Supersedes" ":" SP Supersedes-content
   User-Agent-content   = product *( CFWS product )
   User-Agent-header    = "User-Agent" ":" SP User-Agent-content
                             *( ";" extension-parameter )
   Xref-content         = [CFWS] server-name 1*( CFWS location ) [CFWS]
   Xref-header          = "Xref" ":" SP Xref-content
                             *( ";" extension-parameter )

Appendix B.3.2 - Control-message outlines

   control-message      = <empty> /
                          Newgroup-message /
                          Rmgroup-message /
                          Mvgroup-message /
                          Checkgroup-message /
                          Cancel-message /
                          Ihave-message /

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   Cancel-arguments     = CFWS msg-id [CFWS]
   Cancel-message       = "cancel" Cancel-arguments
   Checkgroup-arguments = [ chkscope ] [ chksernr ]
   Checkgroup-message   = "checkgroups" Checkgroup-arguments
   Ihave-arguments      = relayer-name
   Ihave-message        = "ihave" Ihave-arguments
   Mvgroup-arguments    = CFWS newsgroup-name CFWS newsgroup-name
                             [ CFWS newgroup-flag ]
   Mvgroup-message      = "mvgroup" Mvgroup-arguments
   Newgroup-arguments   = CFWS newsgroup-name [ CFWS newgroup-flag ]
   Newgroup-message     = "newgroup" Newgroup-arguments
   Rmgroup-arguments    = CFWS newsgroup-name
   Rmgroup-message      = "rmgroup" Rmgroup-arguments
   Sendme-arguments     = Ihave-arguments
   Sendme-message       = "sendme" Sendme-arguments

Appendix B.3.3 - Other header rules

   article-locator      = 1*( %x21-27 / %x29-3A / %x3C-7E )
                                  ; US-ASCII printable characters
                                  ; except'(' and ';'
   article-size         = 1*DIGIT
   back-reference       = %x52.65.3A.20
                                  ; which is a case-sensitive "Re: "
   batch                = 1*( batch-header article )
   batch-header         = "#!" SP rnews SP article-size CRLF
   checkgroups-body     = *( valid-group CRLF )
   chkscope             = 1*( CFWS ["!"] newsgroup-name )
   chksernr             = CFWS "#" 1*DIGIT
   component            = 1*component-grapheme
   component-grapheme   = DIGIT / ALPHA / "+" / "-" / "_"
   copy-addr            = address-list
   dist-delim           = ","
   distribution         = [FWS] distribution-name [FWS]
   distribution-name    = ALPHA 1*distribution-rest
   distribution-rest    = ALPHA / "+" / "-" / "_"
   groupinfo-body       = [ newsgroups-tag CRLF ]
                             newsgroups-line CRLF
3  hex4                 = 1*4HEXDIG
3  hexpart              = hexseq / hexseq "::" [ hexseq ] /
                          "::" [ hexseq ]
3  hexseq               = hex4 *( ":" hex4 )
   host-value           = dot-atom /
                          [ dot-atom ":" ]
                            ( IPv4address / IPv6address )
                            ; see  [RFC 2373]
2  id-left              = dot-atom-text / no-fold-quote
2  id-right             = dot-atom-text / no-fold-literal
   ihave-body           = *( msg-id CRLF )
3  IPv4address          = 1*3DIGIT "." 1*3DIGIT "."
                             1*3DIGIT "." 1*3DIGIT
3  IPv6address          = hexpart [ ":" IPv4address ]

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   location             = newsgroup-name ":" article-locator
   mdtext               = NO-WS-CTL /      ; Non white space controls
                          %d33-61 /        ; The rest of the US-ASCII
                          %d63-90 /        ; characters not including
                          %d94-126         ; ">", "[", "]", or "\"
   moderation-flag      = %x28.4D.6F.
                             ; case sensitive "(Moderated)"
   mqspecial            = "(" / ")" /      ; same as specials except
                          "<" /            ; "\" and DQUOTE quoted
                          "[" / "]" /      ; and ">" omitted
                          ":" / ";" /
                          "@" / "\\" /
                          "," / "." /
                          "\" DQUOTE
   mqtext               = NO-WS-CTL /      ; all of <text> except
                          %d33 /           ; SP, HTAB, "\", ">"
                          %d35-61 /        ; and DQUOTE
                          %d63-91 /
2* msg-id               = "<" id-left "@" id-right ">"
   newgroup-flag        = "moderated"
                        = utext *( *WSP utext )
   newsgroup-name       = component *( "." component )
   newsgroups-line      = newsgroup-name
                             [ 1*HTAB newsgroup-description ]
                             [ 1*WSP moderation-flag ]
   newsgroups-tag       = %x46.6F.72 SP %x79.6F.75.72 SP
                             %x6E. SP
                             ; case sensitive
                             ; "For your newsgroups file:"
   ng-delim             = ","
2* no-fold-literal      = "[" *( mdtext / "\[" / "\]" / "\\" ) "]"
2* no-fold-quote        = DQUOTE
                             *( mqtext / "\\" / "\" DQUOTE )
                             *( mqtext / "\\" / "\" DQUOTE )
   path-delimiter       = "/" / "?" / "%" / "," / "!"
   path-identity        = ( ALPHA / DIGIT )
                             *( ALPHA / DIGIT / "-" / "." / ":" / "_" )
                        = <a parameter with attribute "posting-account"
                           and any value>
                        = <a parameter with attribute "posting-date"
                           and value some date-time>
                        = <a parameter with attribute "posting-host"
                           and value some host-value>
                        = <a parameter with attribute "logging-data"
                           and any value>

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                        = <a parameter with attribute "sender"
                           and value some sender-value>
   product              = [CFWS] token [CFWS] [ "/" product-version ]
   product-version      = [CFWS] token [CFWS]
   pure-subject         = unstructured
   relayer-name         = path-identity
   rnews                = %x72.6E.65.77.73 ; case sensitive "rnews"
   sender-value         = mailbox / "verified"
   sendme-body          = ihave-body
   server-name          = path-identity
   tail-entry           = path-identity
   valid-group          = newsgroups-line

Appendix C - Notices

Intellectual Property

   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; neither does it represent that it
   has made any effort to identify any such rights.  Information on the
   IETF's procedures with respect to rights in standards-track and
   standards-related documentation can be found in BCP-11.  Copies of
   claims of rights made available for publication and any assurances of
   licenses to be made available, or the result of an attempt made to
   obtain a general license or permission for the use of such
   proprietary rights by implementors or users of this specification can
   be obtained from the IETF Secretariat.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which may cover technology that may be required to practice
   this standard.  Please address the information to the IETF Executive

Full Copyright Statement

   Copyright (C) The Internet Society (2002). All Rights Reserved

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the  purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than

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   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an

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