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Versions: (draft-melnikov-eai-rfc5337bis) 00 01 02 03 04 05 06 RFC 6533

Network Working Group                                     T. Hansen, Ed.
Internet-Draft                                         AT&T Laboratories
Obsoletes: 5337 (if approved)                                  C. Newman
Updates: 3461, 3462, 3464, 3798                                   Oracle
(if approved)                                                A. Melnikov
Intended status: Standards Track                               Isode Ltd
Expires: May 17, 2012                                  November 14, 2011


    Internationalized Delivery Status and Disposition Notifications
                    draft-ietf-eai-rfc5337bis-dsn-06

Abstract

   Delivery status notifications (DSNs) are critical to the correct
   operation of an email system.  However, the existing Draft Standards
   (RFC 3461, RFC 3462, RFC 3464) are presently limited to US-ASCII text
   in the machine-readable portions of the protocol.  This specification
   adds a new address type for international email addresses so an
   original recipient address with non-US-ASCII characters can be
   correctly preserved even after downgrading.  This also provides
   updated content return media types for delivery status notifications
   and message disposition notifications to support use of the new
   address type.

   This document extends RFC 3461, RFC 3462, RFC 3464, and RFC 3798.  It
   replaces the experimental RFC 5337.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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 progress."

   This Internet-Draft will expire on May 17, 2012.

Copyright Notice

   Copyright (c) 2011 IETF Trust and the persons identified as the



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   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions Used in This Document  . . . . . . . . . . . . . .  3
   3.  UTF-8 Address Type . . . . . . . . . . . . . . . . . . . . . .  3
   4.  UTF-8 Delivery Status Notifications  . . . . . . . . . . . . .  6
     4.1.  The message/global-delivery-status Media Type  . . . . . .  6
     4.2.  The message/global Media Type  . . . . . . . . . . . . . .  9
     4.3.  The message/global-headers Media Type  . . . . . . . . . .  9
     4.4.  Using These Media Types with multipart/report  . . . . . .  9
     4.5.  Additional Requirements on SMTP Servers  . . . . . . . . .  9
   5.  UTF-8 Message Disposition Notifications  . . . . . . . . . . . 10
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
     6.1.  UTF-8 Mail Address Type Registration . . . . . . . . . . . 11
     6.2.  Update to 'smtp' Diagnostic Type Registration  . . . . . . 11
     6.3.  message/global-headers . . . . . . . . . . . . . . . . . . 12
     6.4.  message/global-delivery-status . . . . . . . . . . . . . . 13
     6.5.  message/global-disposition-notification  . . . . . . . . . 14
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 15
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 16
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 17
   Appendix A.  Changes Since RFC 5337  . . . . . . . . . . . . . . . 18
   Appendix B.  Acknowledgements  . . . . . . . . . . . . . . . . . . 18















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1.  Introduction

   When an email message is transmitted using the UTF8SMTP
   [I-D.ietf-eai-rfc5336bis] extension and Internationalized Email
   Headers [I-D.ietf-eai-rfc5335bis], it is sometimes necessary to
   return that message or generate a Message Disposition Notification
   (MDN) [RFC3798].  As a message sent to multiple recipients can
   generate a status and disposition notification for each recipient, it
   is helpful if a client can correlate these notifications based on the
   recipient address it provided; thus, preservation of the original
   recipient is important.  This specification describes how to preserve
   the original recipient and updates the MDN and DSN formats to support
   the new address types.

   NOTE: While this specification updates the experimental versions of
   this protocol by removing certain constructs (e.g., the "<addr
   <addr>>" address syntax is no longer permitted), the name of the
   Address Type "UTF-8" and the media type names message/global,
   message/global-delivery-status and message/global-headers have not
   been changed.

   This specification is a revision of and replacement for [RFC5337].
   Section 6 of [I-D.ietf-eai-frmwrk-4952bis] describes the change in
   approach between this specification and the previous version.

2.  Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

   The formal syntax uses the Augmented Backus-Naur Form (ABNF)
   [RFC5234] notation including the core rules defined in Appendix B of
   RFC 5234 [RFC5234] and the UTF-8 syntax rules in Section 4 of
   [RFC3629].

3.  UTF-8 Address Type

   An Extensible Message Format for Delivery Status Notifications
   [RFC3464] defines the concept of an address type.  The address format
   introduced in Internationalized Email Headers
   [I-D.ietf-eai-rfc5335bis] is a new address type.  The syntax for the
   new address type in the context of status notifications is specified
   at the end of this section.

   An SMTP [RFC5321] server that advertises both the UTF8SMTP extension
   [I-D.ietf-eai-rfc5336bis] and the DSN extension [RFC3461] MUST accept
   a UTF-8 address type in the ORCPT parameter including 8-bit UTF-8



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   characters.  This address type also includes a 7-bit encoding
   suitable for use in a message/delivery-status body part or an ORCPT
   parameter sent to an SMTP server that does not advertise UTF8SMTP.

   This address type has 3 forms: utf-8-addr-xtext, utf-8-addr-unitext,
   and utf-8-address.  Only the first form is 7-bit safe (only uses US-
   ASCII characters).

   The utf-8-address form is only suitable for use in newly defined
   protocols capable of native representation of 8-bit characters.  That
   is, the utf-8-address form MUST NOT be used:

   1.  in the ORCPT parameter when the SMTP server doesn't advertise
       support for UTF8SMTP (utf-8-addr-xtext MUST be used instead); or

   2.  the SMTP server supports UTF8SMTP, but the address contains US-
       ASCII characters not permitted in the ORCPT parameter (e.g., the
       ORCPT parameter forbids unencoded SP and the = character),
       (either utf-8-addr-unitext or utf-8-addr-xtext MUST be used
       instead); or

   3.  in a 7-bit transport environment including a message/
       delivery-status Original-Recipient or Final-Recipient field,
       (utf-8-addr-xtext MUST be used instead).

   The utf-8-address form MAY be used in the ORCPT parameter when the
   SMTP server also advertises support for UTF8SMTP and the address
   doesn't contain any US-ASCII characters not permitted in the ORCPT
   parameter.  It SHOULD be used in a message/global-delivery-status
   Original-Recipient or Final-Recipient DSN field, or in an Original-
   Recipient header field [RFC3798] if the message is a UTF8SMTP
   message.

   In addition, the utf-8-addr-unitext form can be used anywhere where
   the utf-8-address form is allowed.

   When used in the ORCPT parameter, the UTF-8 address type requires
   that US-ASCII CTLs, SP, \, +, and = be encoded using 'unitext'
   encoding (see below).  This is described by the utf-8-addr-xtext and
   utf-8-addr-unitext forms in the ABNF below.  The 'unitext' encoding
   uses "\x{HEXPOINT}" syntax (EmbeddedUnicodeChar in the ABNF below)
   for encoding any Unicode character outside of US-ASCII range, as well
   as for encoding CTLs, SP, \, +, and =.  HEXPOINT is 2 to 6
   hexadecimal digits.  This encoding avoids the need to use the xtext
   encoding described in [RFC3461], as any US-ASCII characters that
   needs to be escaped using xtext encoding never appear in any unitext
   encoded string.  When sending data to a UTF8SMTP capable server,
   native UTF-8 characters SHOULD be used instead of the



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   EmbeddedUnicodeChar syntax described in details below.  When sending
   data to an SMTP server that does not advertise UTF8SMTP, then the
   EmbeddedUnicodeChar syntax MUST be used instead of UTF-8.

   When the ORCPT parameter is placed in a message/
   global-delivery-status Original-Recipient field, the 'utf-8-addr-
   xtext' form of the UTF-8 address type SHOULD be converted to the
   'utf-8-address' form (see the ABNF below) by removing the 'unitext'
   encoding.  However, if an address is labeled with the UTF-8 address
   type but does not conform to utf-8 syntax, then it MUST be copied
   into the message/global-delivery-status field without alteration.

   The ability to encode characters with the EmbeddedUnicodeChar
   encodings should be viewed as a transitional mechanism and avoided
   when possible.  It is hoped that as systems lacking support for
   UTF8SMTP become less common over time, these encodings can eventually
   be phased out.

   In the ABNF below, all productions not defined in this document are
   defined in Appendix B of [RFC5234], in Section 4 of [RFC3629], or in
   [RFC3464].

   utf-8-type-addr     = "utf-8;" utf-8-enc-addr

   utf-8-address       = Mailbox
     ; Mailbox as defined in [I-D.ietf-eai-rfc5336bis].

   utf-8-enc-addr      = utf-8-addr-xtext /
                         utf-8-addr-unitext /
                         utf-8-address

   utf-8-addr-xtext    = 1*(QCHAR / EmbeddedUnicodeChar)
                         ; 7bit form of utf-8-addr-unitext.
                         ; Safe for use in the ORCPT [RFC3461]
                         ; parameter even when UTF8SMTP SMTP
                         ; extension is not advertised.

   utf-8-addr-unitext  = 1*(QUCHAR / EmbeddedUnicodeChar)
                       ; MUST follow utf-8-address ABNF when
                       ; dequoted.
                       ; Safe for using in the ORCPT [RFC3461]
                       ; parameter when UTF8SMTP SMTP extension
                       ; is also advertised.

   QCHAR              = %x21-2a / %x2c-3c / %x3e-5b / %x5d-7e
                       ; US-ASCII printable characters except
                       ; CTLs, SP, '\', '+', '='.




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   QUCHAR              = QCHAR / UTF8-2 / UTF8-3 / UTF8-4
                       ; US-ASCII printable characters except
                       ; CTLs, SP, '\', '+' and '=', plus
                       ; other Unicode characters encoded in UTF-8

   EmbeddedUnicodeChar =   %x5C.78 "{" HEXPOINT "}"
                       ; starts with "\x"

   HEXPOINT = ( ( "0"/"1" ) %x31-39 ) / "10" / "20" /
              "2B" / "3D" / "7F" /         ; all xtext-specials
              "5C" / (HEXDIG8 HEXDIG) /    ; 2 digit forms
              ( NZHEXDIG 2(HEXDIG) ) /     ; 3 digit forms
              ( NZDHEXDIG 3(HEXDIG) ) /    ; 4 digit forms excluding
              ( "D" %x30-37 2(HEXDIG) ) /  ; ... surrogate
              ( NZHEXDIG 4(HEXDIG) ) /     ; 5 digit forms
              ( "10" 4*HEXDIG )            ; 6 digit forms
              ; represents either "\" or a Unicode code point outside
              ; the US-ASCII repertoire

   HEXDIG8             = %x38-39 / "A" / "B" / "C" / "D" / "E" / "F"
                       ; HEXDIG excluding 0-7
   NZHEXDIG            = %x31-39 / "A" / "B" / "C" / "D" / "E" / "F"
                       ; HEXDIG excluding "0"
   NZDHEXDIG           = %x31-39 / "A" / "B" / "C" / "E" / "F"
                       ; HEXDIG excluding "0" and "D"

4.  UTF-8 Delivery Status Notifications

   A traditional delivery status notification [RFC3464] comes in a
   three-part multipart/report [RFC3462] container, where the first part
   is human-readable text describing the error, the second part is a
   7-bit-only message/delivery-status, and the optional third part is
   used for content (message/rfc822) or header (text/rfc822-headers)
   return.  As the present standard DSN format does not permit the
   return of undeliverable UTF8SMTP messages, three new media types are
   needed.  ([RFC5337] introduced experimental versions of these media
   types.)

4.1.  The message/global-delivery-status Media Type

   The first type, message/global-delivery-status, has the syntax of
   message/delivery-status with three modifications.  First, the charset
   for message/global-delivery-status is UTF-8, and thus any field MAY
   contain UTF-8 characters when appropriate (see the ABNF below).  In
   particular, the Diagnostic-Code field MAY contain UTF-8 as described
   in UTF8SMTP [I-D.ietf-eai-rfc5336bis]; the Diagnostic-Code field
   SHOULD be in i-default language [RFC2277].  Second, systems
   generating a message/global-delivery-status body part SHOULD use the



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   utf-8-address form of the UTF-8 address type for all addresses
   containing characters outside the US-ASCII repertoire.  These systems
   SHOULD up-convert the utf-8-addr-xtext or the utf-8-addr-unitext form
   of a UTF-8 address type in the ORCPT parameter to the utf-8-address
   form of a UTF-8 address type in the Original-Recipient field.  Third,
   an optional field called Localized-Diagnostic is added.  Each
   instance includes a language tag [RFC5646] and contains text in the
   specified language.  This is equivalent to the text part of the
   Diagnostic-Code field.  All instances of Localized-Diagnostic MUST
   use different language tags.  The ABNF for message/
   global-delivery-status is specified below.

   In the ABNF below, all productions not defined in this document are
   defined in Appendix B of [RFC5234], in Section 4 of [RFC3629], or in
   [RFC3464].  Note that <text-fixed> is the same as <text> from
   [RFC5322], but without <obs-text>.  If or when RFC 5322 is updated to
   disallow <obs-text>, this should become just <text>.  Also, if or
   when RFC 5322 is updated to disallow control characters in <text>,
   this should become a reference to that update instead.
































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   utf-8-delivery-status-content = per-message-fields
                         1*( CRLF utf-8-per-recipient-fields )
        ; "per-message-fields" remains unchanged from the definition
        ; in RFC 3464, except for the "extension-field"
        ; which is updated below.

   utf-8-per-recipient-fields =
         [ original-recipient-field CRLF ]
         final-recipient-field CRLF
         action-field CRLF
         status-field CRLF
         [ remote-mta-field CRLF ]
         [ diagnostic-code-field CRLF
           *(localized-diagnostic-text-field CRLF) ]
         [ last-attempt-date-field CRLF ]
             [ final-log-id-field CRLF ]
         [ will-retry-until-field CRLF ]
         *( extension-field CRLF )
     ; All fields except for "original-recipient-field",
     ; "final-recipient-field", "diagnostic-code-field"
     ; and "extension-field" remain unchanged from
     ; the definition in RFC 3464.

   generic-address =/ utf-8-enc-addr
     ; Only allowed with the "utf-8" address-type.
     ; Updates Section 3.2.3 of RFC3798
     ;
     ; This indirectly updates "original-recipient-field"
     ; and "final-recipient-field"

   diagnostic-code-field =
        "Diagnostic-Code" ":" diagnostic-type ";" *text-fixed

   localized-diagnostic-text-field =
        "Localized-Diagnostic" ":" Language-Tag ";" *utf8-text
     ; "Language-Tag" is a language tag as defined in [RFC5646].

   extension-field =/ extension-field-name ":" *utf8-text
     ; Updates Section 7 of RFC3798

   text-fixed = %d1-9 /      ; Any US-ASCII character except for NUL,
                %d11 /       ; CR and LF
                %d12 /       ; See note above about <text-fixed>
                %d14-127

   utf8-text = text-fixed / UTF8-non-ascii

   UTF8-non-ascii   = UTF8-2 / UTF8-3 / UTF8-4



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4.2.  The message/global Media Type

   The second type, used for returning the content, is message/global
   which is similar to message/rfc822, except it contains a message with
   UTF-8 headers.  This media type is described in
   [I-D.ietf-eai-rfc5335bis].

4.3.  The message/global-headers Media Type

   The third type, used for returning the headers, is message/
   global-headers and contains only the UTF-8 header fields of a message
   (all lines prior to the first blank line in a UTF8SMTP message).
   Unlike message/global, this body part provides no difficulties for
   the present infrastructure.

4.4.  Using These Media Types with multipart/report

   Note that as far as a multipart/report [RFC3462] container is
   concerned, message/global-delivery-status, message/global, and
   message/global-headers MUST be treated as equivalent to message/
   delivery-status, message/rfc822, and text/rfc822-headers.  That is,
   implementations processing multipart/report MUST expect any
   combinations of the 6 media types mentioned above inside a multipart/
   report media type.

   All three new types will typically use the "8bit" Content-Transfer-
   Encoding.  (In the event all content is 7-bit, the equivalent
   traditional types for delivery status notifications MAY be used.  For
   example, if information in message/global-delivery-status part can be
   represented without any loss of information as message/
   delivery-status, then the message/delivery-status body part may be
   used.)  Note that [I-D.ietf-eai-rfc5335bis] relaxed a restriction
   from MIME [RFC2046] regarding the use of Content-Transfer-Encoding in
   new "message" subtypes.  This specification explicitly allows the use
   of Content-Transfer-Encoding in message/global-headers and message/
   global-delivery-status.  This is not believed to be problematic as
   these new media types are intended primarily for use by newer systems
   with full support for 8-bit MIME and UTF-8 headers.

4.5.  Additional Requirements on SMTP Servers

   If an SMTP server that advertises both UTF8SMTP and DSN needs to
   return an undeliverable UTF8SMTP message, then it has two choices for
   encapsulating the UTF8SMTP message when generating the corresponding
   multipart/report:

      If the return path SMTP server does not support UTF8SMTP, then the
      undeliverable body part and headers MUST be encoded using a 7-bit



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      Content-Transfer-Encoding such as "base64" or "quoted-printable"
      [RFC2045], as detailed in Section 4.

      Otherwise, "8bit" Content-Transfer-Encoding can be used.

5.  UTF-8 Message Disposition Notifications

   Message Disposition Notifications [RFC3798] have a similar design and
   structure to DSNs.  As a result, they use the same basic return
   format.  When generating an MDN for a UTF-8 header message, the third
   part of the multipart/report contains the returned content (message/
   global) or header (message/global-headers), same as for DSNs.  The
   second part of the multipart/report uses a new media type, message/
   global-disposition-notification, which has the syntax of message/
   disposition-notification with two modifications.  First, the charset
   for message/global-disposition-notification is UTF-8, and thus any
   field MAY contain UTF-8 characters when appropriate (see the ABNF
   below).  (In particular, the failure-field, the error-field, and the
   warning-field MAY contain UTF-8.  These fields SHOULD be in i-default
   language [RFC2277].)  Second, systems generating a message/
   global-disposition-notification body part (typically a mail user
   agent) SHOULD use the UTF-8 address type for all addresses containing
   characters outside the US-ASCII repertoire.

   The MDN specification also defines the Original-Recipient header
   field, which is added with a copy of the contents of ORCPT at
   delivery time.  When generating an Original-Recipient header field, a
   delivery agent writing a UTF-8 header message in native format SHOULD
   convert the utf-8-addr-xtext or the utf-8-addr-unitext form of a
   UTF-8 address type in the ORCPT parameter to the corresponding utf-8-
   address form.

   The MDN specification also defines the Disposition-Notification-To
   header field, which is an address header field and thus follows the
   same 8-bit rules as other address header fields such as "From" and
   "To" when used in a UTF-8 header message.















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     ; ABNF for "original-recipient-header", "original-recipient-field",
     ; and "final-recipient-field" from RFC 3798 is implicitly updated
     ; as they use the updated "generic-address" as defined in
     ; Section 4 of this document.

   failure-field = "Failure" ":" *utf8-text
     ; "utf8-text" is defined in Section 4 of this document.

   error-field = "Error" ":" *utf8-text
     ; "utf8-text" is defined in Section 4 of this document.

   warning-field = "Warning" ":" *utf8-text
     ; "utf8-text" is defined in Section 4 of this document.

6.  IANA Considerations

   This specification does not create any new IANA registries.  However,
   the following items are registered as a result of this document.

6.1.  UTF-8 Mail Address Type Registration

   The mail address type registry was created by [RFC3464].  The
   registration template response follows:

   (a) The proposed address-type name.

       UTF-8

   (b) The syntax for mailbox addresses of this type, specified using
       BNF, regular expressions, ASN.1, or other non-ambiguous language.

       See Section 3.

   (c) If addresses of this type are not composed entirely of graphic
       characters from the US-ASCII repertoire, a specification for how
       they are to be encoded as graphic US-ASCII characters in a DSN
       Original-Recipient or Final-Recipient DSN field.

       This address type has 3 forms (as defined in Section 3): utf-8-
       addr-xtext, utf-8-addr-unitext, and utf-8-address.  Only the
       first form is 7-bit safe.

6.2.  Update to 'smtp' Diagnostic Type Registration

   The mail diagnostic type registry was created by [RFC3464] and
   updated by [RFC5337] and this specification.  The registration for
   the 'smtp' diagnostic type should be updated to reference RFC XXXX in
   addition to [RFC3464] and [RFC5337].



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   When the 'smtp' diagnostic type is used in the context of a message/
   delivery-status body part, it remains as presently defined.  When the
   'smtp' diagnostic type is used in the context of a message/
   global-delivery-status body part, the codes remain the same, but the
   text portion MAY contain UTF-8 characters.

6.3.  message/global-headers

   Type name:  message

   Subtype name:  global-headers

   Required parameters:  none

   Optional parameters:  none

   Encoding considerations:  This media type contains Internationalized
      Email Headers [I-D.ietf-eai-rfc5335bis] with no message body.
      Whenever possible, the 8-bit content transfer encoding SHOULD be
      used.  When this media type passes through a 7-bit-only SMTP
      infrastructure it MAY be encoded with the base64 or quoted-
      printable content transfer encoding.

   Security considerations:  See Section 7.

   Interoperability considerations:  It is important that this media
      type is not converted to a charset other than UTF-8.  As a result,
      implementations MUST NOT include a charset parameter with this
      media type.  Although it might be possible to downconvert this
      media type to the text/rfc822-header media type, such conversion
      is discouraged as it loses information.

   Published specification:  RFC XXXX

   Applications that use this media type:  UTF8SMTP servers and email
      clients that support multipart/report generation or parsing.

   Additional information:

   Magic number(s):  none

   File extension(s):  In the event this is saved to a file, the
      extension ".u8hdr" is suggested.

   Macintosh file type code(s):  The 'TEXT' type code is suggested as
      files of this type are typically used for diagnostic purposes and
      suitable for analysis in a UTF-8 aware text editor.  A uniform
      type identifier (UTI) of "public.utf8-email-message-header" is



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      suggested.  This type conforms to "public.utf8-plain-text" and
      "public.plain-text".

   Person & email address to contact for further information:  See the
      Authors' Addresses section of this document.

   Intended usage:  COMMON

   Restrictions on usage:  This media type contains textual data in the
      UTF-8 charset.  It typically contains octets with the 8th bit set.
      As a result, a transfer encoding is required when a 7-bit
      transport is used.

   Author:  See the Authors' Addresses section of this document.

   Change controller:  IETF Standards Process

6.4.  message/global-delivery-status

   Type name:  message

   Subtype name:  global-delivery-status

   Required parameters:  none

   Optional parameters:  none

   Encoding considerations:  This media type contains delivery status
      notification attributes in the UTF-8 charset.  The 8-bit content
      transfer encoding MUST be used with this content-type, unless it
      is sent over a 7-bit transport environment in which case quoted-
      printable or base64 may be necessary.

   Security considerations:  See Section 7

   Interoperability considerations:  This media type provides
      functionality similar to the message/delivery-status content-type
      for email message return information.  Clients of the previous
      format will need to be upgraded to interpret the new format;
      however, the new media type makes it simple to identify the
      difference.

   Published specification:  RFC XXXX

   Applications that use this media type:  SMTP servers and email
      clients that support delivery status notification generation or
      parsing.




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   Additional information:

   Magic number(s):  none

   File extension(s):  The extension ".u8dsn" is suggested.

   Macintosh file type code(s):  A uniform type identifier (UTI) of
      "public.utf8-email-message-delivery-status" is suggested.  This
      type conforms to "public.utf8-plain-text".

   Person & email address to contact for further information:  See the
      Authors' Addresses section of this document.

   Intended usage:  COMMON

   Restrictions on usage:  This is expected to be the second part of a
      multipart/report.

   Author:  See the Authors' Addresses section of this document.

   Change controller:  IETF Standards Process

6.5.  message/global-disposition-notification

   Type name:  message

   Subtype name:  global-disposition-notification

   Required parameters:  none

   Optional parameters:  none

   Encoding considerations:  This media type contains disposition
      notification attributes in the UTF-8 charset.  The 8-bit content
      transfer encoding MUST be used with this content-type, unless it
      is sent over a 7-bit transport environment in which case quoted-
      printable or base64 may be necessary.

   Security considerations:  See Section 7.

   Interoperability considerations:  This media type provides
      functionality similar to the message/disposition-notification
      content-type for email message disposition information.  Clients
      of the previous format will need to be upgraded to interpret the
      new format; however, the new media type makes it simple to
      identify the difference.





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   Published specification:  RFC XXXX

   Applications that use this media type:  Email clients or servers that
      support message disposition notification generation or parsing.

   Additional information:

   Magic number(s):  none

   File extension(s):  The extension ".u8mdn" is suggested.

   Macintosh file type code(s):  A uniform type identifier (UTI) of
      "public.utf8-email-message-disposition-notification" is suggested.
      This type conforms to "public.utf8-plain-text".

   Person & email address to contact for further information:  See the
      Authors' Addresses section of this document.

   Intended usage:  COMMON

   Restrictions on usage:  This is expected to be the second part of a
      multipart/report.

   Author:  See the Authors' Addresses section of this document.

   Change controller:  IETF Standards Process

7.  Security Considerations

   Automated use of report types without authentication presents several
   security issues.  Forging negative reports presents the opportunity
   for denial-of-service attacks when the reports are used for automated
   maintenance of directories or mailing lists.  Forging positive
   reports may cause the sender to incorrectly believe a message was
   delivered when it was not.

   Malicious users can generate report structures designed to trigger
   coding flaws in report parsers.  Report parsers need to use secure
   coding techniques to avoid the risk of buffer overflow or denial-of-
   service attacks against parser coding mistakes.  Code reviews of such
   parsers are also recommended.

   Malicious users of the email system regularly send messages with
   forged envelope return paths, and these messages trigger delivery
   status reports that result in a large amount of unwanted traffic on
   the Internet.  Many users choose to ignore delivery status
   notifications because they are usually the result of "blowback" from
   forged messages and thus never notice when messages they sent go



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   undelivered.  As a result, support for correlation of delivery status
   and message disposition notification messages with sent-messages has
   become a critical feature of mail clients and possibly mail stores if
   the email infrastructure is to remain reliable.  In the short term,
   simply correlating message-IDs may be sufficient to distinguish true
   status notifications from those resulting from forged originator
   addresses.  But in the longer term, including cryptographic signature
   material that can securely associate the status notification with the
   original message is advisable.

   As this specification permits UTF-8 in additional fields, the
   security considerations of UTF-8 [RFC3629] apply.

8.  References

8.1.  Normative References

   [RFC2119]                      Bradner, S., "Key words for use in
                                  RFCs to Indicate Requirement Levels",
                                  BCP 14, RFC 2119, March 1997.

   [RFC2277]                      Alvestrand, H., "IETF Policy on
                                  Character Sets and Languages", BCP 18,
                                  RFC 2277, January 1998.

   [RFC3461]                      Moore, K., "Simple Mail Transfer
                                  Protocol (SMTP) Service Extension for
                                  Delivery Status Notifications (DSNs)",
                                  RFC 3461, January 2003.

   [RFC3462]                      Vaudreuil, G., "The Multipart/Report
                                  Content Type for the Reporting of Mail
                                  System Administrative Messages",
                                  RFC 3462, January 2003.

   [RFC3464]                      Moore, K. and G. Vaudreuil, "An
                                  Extensible Message Format for Delivery
                                  Status Notifications", RFC 3464,
                                  January 2003.

   [RFC3629]                      Yergeau, F., "UTF-8, a transformation
                                  format of ISO 10646", STD 63,
                                  RFC 3629, November 2003.

   [RFC3798]                      Hansen, T. and G. Vaudreuil, "Message
                                  Disposition Notification", RFC 3798,
                                  May 2004.




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   [RFC5646]                      Phillips, A. and M. Davis, "Tags for
                                  Identifying Languages", BCP 47,
                                  RFC 5646, September 2009.

   [RFC5321]                      Klensin, J., "Simple Mail Transfer
                                  Protocol", RFC 5321, October 2008.

   [RFC5322]                      Resnick, P., Ed., "Internet Message
                                  Format", RFC 5322, October 2008.

   [RFC5234]                      Crocker, D. and P. Overell, "Augmented
                                  BNF for Syntax Specifications: ABNF",
                                  STD 68, RFC 5234, January 2008.

   [I-D.ietf-eai-rfc5335bis]      Yang, A., Steele, S., and N. Freed,
                                  "Internationalized Email Headers",
                                  draft-ietf-eai-rfc5335bis-13 (work in
                                  progress), October 2011.

   [I-D.ietf-eai-rfc5336bis]      Yao, J. and W. MAO, "SMTP Extension
                                  for Internationalized Email",
                                  draft-ietf-eai-rfc5336bis-16 (work in
                                  progress), November 2011.

   [I-D.ietf-eai-frmwrk-4952bis]  Klensin, J. and Y. Ko, "Overview and
                                  Framework for Internationalized
                                  Email",
                                  draft-ietf-eai-frmwrk-4952bis-12 (work
                                  in progress), October 2011.

8.2.  Informative References

   [RFC2045]                      Freed, N. and N. Borenstein,
                                  "Multipurpose Internet Mail Extensions
                                  (MIME) Part One: Format of Internet
                                  Message Bodies", RFC 2045,
                                  November 1996.

   [RFC2046]                      Freed, N. and N. Borenstein,
                                  "Multipurpose Internet Mail Extensions
                                  (MIME) Part Two: Media Types",
                                  RFC 2046, November 1996.

   [RFC5337]                      Newman, C. and A. Melnikov,
                                  "Internationalized Delivery Status and
                                  Disposition Notifications", RFC 5337,
                                  September 2008.




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Appendix A.  Changes Since RFC 5337

   Made changes to move from Experimental to Standards Track.  The most
   significant was the removal of an embedded alternative ASCII address
   within a utf-8-address, and reflections of the ABNF changes in
   [I-D.ietf-eai-rfc5336bis].

   Fixed description of utf-8-addr-xtext and utf-8-addr-unitext.

   References to Downgrade and uMailbox removed/fixed.

   ABNF changes and errata suggested by Alfred Hoenes.

   Minor changes to MIME type references.

   Other minor corrections.

Appendix B.  Acknowledgements

   Many thanks for input provided by Pete Resnick, James Galvin, Ned
   Freed, John Klensin, Harald Alvestrand, Frank Ellermann, SM, Alfred
   Hoenes, Kazunori Fujiwara, and members of the EAI WG to help solidify
   this proposal.

Authors' Addresses

   Tony Hansen (editor)
   AT&T Laboratories
   200 Laurel Ave.
   Middletown, NJ  07748
   USA

   EMail: tony+eaidsn@maillennium.att.com


   Chris Newman
   Oracle
   800 Royal Oaks
   Monrovia, CA  91016-6347
   US

   EMail: chris.newman@oracle.com









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   Alexey Melnikov
   Isode Ltd
   5 Castle Business Village
   36 Station Road
   Hampton, Middlesex  TW12 2BX
   UK

   EMail: Alexey.Melnikov@isode.com











































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