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Network Working Group                                    J. Klensin, Ed.
Internet-Draft                                            March 30, 2020
Intended status: Standards Track
Expires: October 1, 2020


         Applicability Statement for IETF Core Email Protocols
                    draft-klensin-email-core-as-00

Abstract

   Electronic mail is one of the oldest Internet applications that is
   still in very active use.  While the basic protocols and formats for
   mail transport and message formats have evolved slowly over the
   years, events and thinking in more recent years have supplemented
   those core protocols with additional features and suggestions for
   their use.  This Applicability Statement describes the relationship
   among many of those protocols and provides guidance and makes
   recommendations for the use of features of the core protocols.

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 https://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 October 1, 2020.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://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



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   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Applicability of Some SMTP Provisions . . . . . . . . . . . .   3
   3.  Applicability of Message Format Provisions  . . . . . . . . .   3
   4.  MIME and Its Implications . . . . . . . . . . . . . . . . . .   3
   5.  Other Stuff . . . . . . . . . . . . . . . . . . . . . . . . .   4
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   4
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   In its current form, this draft is a placeholder and beginning of an
   outline for the Applicability Statement that has been discussed as a
   complement for proposed revisions of the base protocol specifications
   for SMTP [RFC5321] (being revised as ID.RFC5321bis [ID.RFC5321bis])
   and Internet Message Format [RFC5322] (being revised as ID.RFC5322bis
   [ID.RFC5322bis]).  Among other things, it is expected to capture
   topics that a potential WG concludes are important but that should
   not become part of those core documents.

   As discussed in RFC 2026 [RFC2026],

      "An Applicability Statement specifies how, and under what
      circumstances, one or more TSs may be applied to support a
      particular Internet capability."

   That form of a standards track document is appropriate because one of
   the roles of such a document is to explain the relationship among
   technical specification, describe how they are used together, and
   make statements about what is "required, recommended, or elective".

   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 RFC 2119 [RFC2119] and
   RFC 8174 [RFC8174].






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2.  Applicability of Some SMTP Provisions

   Over the years since RFC 5321 was published in October 2008, usage of
   SMTP has evolved, machines and network speeds have increased, and the
   frequency with which SMTP senders and receivers have to be prepared
   to deal with systems that are disconnected from the Internet for long
   periods or that require many hops to reach has decreased.  During the
   same period, the IETF has become much more sensitive to privacy and
   security issues and the need to be more resistant or robust against
   spam and other attacks.  In addition SMTP (and Message Format)
   extensions have been introduced that are expected to evolve the
   Internet's mail system to better accommodate environments in which
   Basic Latin Script is not the norm.

   This section describes adjustments that may be appropriate for SMTP
   under various circumstances and discusses the applicability of other
   protocols that represent newer work or that are intended to deal with
   relatively newer issues.

   [[CREF1: ... Actual content to be supplied after WG consideration.
   ]]

3.  Applicability of Message Format Provisions

   Placeholder:
   I am not sure what, if anything, goes here.  If nothing does, we drop
   the section.

   [[CREF2: ... Actual content to be supplied after WG consideration.]]

4.  MIME and Its Implications

   When the work leading to the original version of the MIME
   specification was completed in 1992 [RFC1341], the intention was that
   it be kept separate from the specification for basic mail headers in
   RFC 822 [RFC0822].  That plan was carried forward into RFC 822's
   successors, RFC 2822 [RFC2822] and RFC 5322 [RFC5322].  The decision
   to do so was different from the one made for SMTP, for which the core
   specification was changed to allow for the extension mechanism
   [RFC1425] which was then incorporated into RFC 5321 and its
   predecessor [RFC2821].

   Various uses of MIME have become nearly ubiquitous in contemporary
   email while others may have fallen into disuse or been repurposed
   from the intent of their original design.

   It may be appropriate to make some clear statements about the
   applicability of MIME and its features.



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5.  Other Stuff

   It is fairly clear that there will be things that do not fit into the
   sections outlined above.  As one example, if the IETF wants to say
   something specific about signatures over headers or what (non-trace)
   headers may reasonably be altered in transit, that may be more
   appropriate to other sections than to any of the three suggested
   above.

6.  Acknowledgments

   ... To be supplied...
   [[CREF3: But don't forget to mention the discussions on the SMTP list
   of the reasons for this document in the last half of 2019. ]]

7.  IANA Considerations

   This memo includes no requests to or actions for IANA.  The IANA
   registries associated with the protocol specifications it references
   are specified in their respective documents.

8.  Security Considerations

   All drafts are required to have a security considerations section and
   this one eventually will.

   ... To be supplied ...

9.  References

9.1.  Normative References

   [RFC2026]  Bradner, S., "The Internet Standards Process -- Revision
              3", BCP 9, RFC 2026, DOI 10.17487/RFC2026, October 1996,
              <https://www.rfc-editor.org/info/rfc2026>.

   [RFC2045]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
              Extensions (MIME) Part One: Format of Internet Message
              Bodies", RFC 2045, DOI 10.17487/RFC2045, November 1996,
              <https://www.rfc-editor.org/info/rfc2045>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.






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   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

9.2.  Informative References

   [ID.RFC5321bis]
              Klensin, J., "Simple Mail Transfer Protocol", December
              2019, <https://datatracker.ietf.org/doc/draft-klensin-
              rfc5321bis/>.

   [ID.RFC5322bis]
              Resnick, P., "Internet Message Format", December 2019,
              <https://datatracker.ietf.org/doc/draft-resnick-
              rfc5322bis/>.

   [RFC0822]  Crocker, D., "STANDARD FOR THE FORMAT OF ARPA INTERNET
              TEXT MESSAGES", STD 11, RFC 822, DOI 10.17487/RFC0822,
              August 1982, <https://www.rfc-editor.org/info/rfc822>.

   [RFC1341]  Borenstein, N. and N. Freed, "MIME (Multipurpose Internet
              Mail Extensions): Mechanisms for Specifying and Describing
              the Format of Internet Message Bodies", RFC 1341,
              DOI 10.17487/RFC1341, June 1992,
              <https://www.rfc-editor.org/info/rfc1341>.

   [RFC1425]  Klensin, J., Freed, N., Ed., Rose, M., Stefferud, E., and
              D. Crocker, "SMTP Service Extensions", February 1993,
              <https://www.rfc-editor.org/info/rfc1425>.

   [RFC2821]  Klensin, J., Ed., "Simple Mail Transfer Protocol",
              RFC 2821, DOI 10.17487/RFC2821, April 2001,
              <https://www.rfc-editor.org/info/rfc2821>.

   [RFC2822]  Resnick, P., Ed., "Internet Message Format", RFC 2822,
              DOI 10.17487/RFC2822, April 2001,
              <https://www.rfc-editor.org/info/rfc2822>.

   [RFC5321]  Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,
              DOI 10.17487/RFC5321, October 2008,
              <https://www.rfc-editor.org/info/rfc5321>.

   [RFC5322]  Resnick, P., Ed., "Internet Message Format", RFC 5322,
              DOI 10.17487/RFC5322, October 2008,
              <https://www.rfc-editor.org/info/rfc5322>.






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Author's Address

   John C Klensin (editor)
   1770 Massachusetts Ave, Ste 322
   Cambridge, MA  02140
   USA

   Phone: +1 617 245 1457
   Email: john-ietf@jck.com










































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