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Versions: 00 01 02 03 04                                                
Individual Submission                                  S. Moonesamy, Ed.
Internet-Draft                                                G. Neufeld
Obsoletes: 2369 (if approved)                                    J. Baer
Intended status: Standards Track                        January 23, 2012
Expires: July 26, 2012


  The Use of URIs as Meta-Syntax for Core Mail List Commands and their
                Transport through Message Header Fields
                     draft-moonesamy-rfc2369bis-03

Abstract

   The mailing list command specification and identification header
   fields are a set of structured fields to be added to email messages
   sent by email distribution lists.  Command header fields typically
   contain URIs (usually including "mailto") locating the relevant
   information or performing the command directly.  The three core
   command header fields described in this document are List-Help, List-
   Subscribe, and List-Unsubscribe.

   There are three other header fields described here which, although
   not as widely applicable, will have utility for a sufficient number
   of mailing lists to justify their formalization here.  These are
   List-Post, List-Owner and List-Archive.

   By including these header fields, mailing list managers can make it
   possible for mail user agents to provide automated tools for users to
   perform list functions.

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 July 26, 2012.

Copyright Notice



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   Copyright (c) 2012 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
   (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
     1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  3
     1.2.  Syntax Notation  . . . . . . . . . . . . . . . . . . . . .  3
     1.3.  Note . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  The Command Syntax . . . . . . . . . . . . . . . . . . . . . .  4
   3.  The List Header Fields . . . . . . . . . . . . . . . . . . . .  5
     3.1.  List-Help  . . . . . . . . . . . . . . . . . . . . . . . .  5
     3.2.  List-Unsubscribe . . . . . . . . . . . . . . . . . . . . .  6
     3.3.  List-Subscribe . . . . . . . . . . . . . . . . . . . . . .  7
     3.4.  List-Post  . . . . . . . . . . . . . . . . . . . . . . . .  8
     3.5.  List-Owner . . . . . . . . . . . . . . . . . . . . . . . .  8
     3.6.  List-Archive . . . . . . . . . . . . . . . . . . . . . . .  9
     3.7.  List-Sequence  . . . . . . . . . . . . . . . . . . . . . . 10
     3.8.  List-Id  . . . . . . . . . . . . . . . . . . . . . . . . . 10
   4.  Supporting Nested Lists  . . . . . . . . . . . . . . . . . . . 10
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 11
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 12
   Appendix A.  Implementation  . . . . . . . . . . . . . . . . . . . 12
   Appendix B.  Changes from RFC 2369 . . . . . . . . . . . . . . . . 12
   Appendix C.  Change Log  . . . . . . . . . . . . . . . . . . . . . 13
     C.1.  Changes between between version -02 and version -03  . . . 13
     C.2.  Changes between between version -01 and version -02  . . . 13
     C.3.  Changes between between version -00 and version -01  . . . 13
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13







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1.  Introduction

   RFC 2369 [RFC2369] defined additional header fields to be added to
   email messages sent by mailing list managers (MLMs).  The significant
   change in this document is the use of Uniform Resource Identifier
   (URI) [RFC3986], instead of Uniform Resource Locator (URL), allowing
   an implementation to parse the common components of a URI reference
   without knowing the scheme-specific requirements of every possible
   identifier.  The content of each new header field is typically a URI
   - usually "mailto" [RFC6068] - which identifies the relevant
   information or performs the command directly.

   These headers fields are optional.  Significant functionality and
   convenience can be gained by including them.  The List-Help header
   field provides an access point to detailed user support information,
   and accommodates almost all existing mailing list managers command
   sets.  The List-Subscribe and List-Unsubscribe header fields provide
   access to two functions commonly requested by mailing list
   subscribers.

   The description of command syntax provided by the header fields can
   be used by mail user agents (MUAs) to provide simplified and
   consistent user access to mailing list functions.  The intent is to
   simplify the user experience, providing a common interface to the
   often cryptic and varied mailing list manager commands.

   Consideration has been given to avoiding the creation of too many
   header fields, while at the same time avoiding the overloading of
   individual header fields and keeping the syntax clear and simple.

   The use of these header fields does not remove the requirement to
   support the -Request command address for mailing lists [RFC2142].

   This document obsoletes RFC 2369 [RFC2369].

1.1.  Terminology

   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].

1.2.  Syntax Notation

   This specification uses the Augmented Backus-Naur Form (ABNF)
   [RFC5234] notation for the formal definitions of the syntax of list
   header fields.





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1.3.  Note

   This Internet-Draft can be discussed on the apps-discuss@ietf.org
   mailing list.  [RFC-Editor: please remove this paragraph]


2.  The Command Syntax

   The list header fields are subject to the encoding and character
   restrictions for mail headers fields as described in [RFC5322].

   The contents of the list header fields mostly consist of angle-
   bracket ('<', '>') enclosed URIs [RFC3986], with internal whitespace
   being ignored. mailing list managers MUST NOT insert whitespace
   within the brackets.  Client applications SHOULD treat any
   whitespace, that might be inserted by poorly behaved mailing list
   managers, as characters to ignore.

   A list of multiple, alternate, URIs MAY be specified by a comma-
   separated list of angle-bracket enclosed URIs.  The URIs have order
   of preference from left to right.  The client application should use
   the left most scheme that it supports, or knows how to access by a
   separate application.  With this mechanism, schemes like http may be
   specified while still providing the basic "mailto" support for those
   clients who do not have access to non-mail scheme.  The client should
   only use one of the available URIs for a command, using another only
   if the first one used failed.

   The use of URIs allows for the use of the syntax with existing URI
   supporting applications.  As the standard for URIs is extended, the
   list header fields will gain the benefit of those extensions.
   Additionally, the use of URIs provides access to multiple schemes
   (such as ftp and http) although it is expected that the "mailto"
   scheme [RFC6068] will be the focus of most use of the list header
   fields.  Use of the schemes should be considered in light of those
   users who do not have access to the specified mechanism.

   Command syntaxes requiring variable fields to be set by the client
   (such as including the user's email address within a command) are not
   supported by this implementation.  However, mailing list managers
   using such syntaxes should still take advantage of the List-Help
   field to provide the user with detailed instructions as needed or -
   perhaps more usefully - provide access to some form of structured
   command interface such as an HTML-based form.

   The additional complications of supporting variable fields within the
   command syntax was determined to be too difficult to support by this
   protocol and would compromise the likelihood of implementation by



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   software authors.

   To allow for future extension, it is recommended that client
   applications follow the guidelines below for handling the contents of
   the header fields described in this document:

   1.  Except where noted for specific header fields, if the content of
       the header field (following any leading whitespace, including
       comments) begins with any character other than the opening angle
       bracket '<', the header field SHOULD be ignored.

   2.  Any characters following an angle bracket enclosed URI SHOULD be
       ignored, unless a comma is the first non-whitespace/comment
       character after the closing angle bracket.

   3.  If a sub-item (comma-separated item) within the field is not an
       angle-bracket enclosed URI, the remainder of the field (the
       current, and all subsequent, sub-items) SHOULD be ignored.


3.  The List Header Fields

   This document presents header fields which will provide the command
   syntax description for the 'core' and key secondary functions of most
   mailing list managers.  The header fields implemented on a given
   mailing list SHOULD be included on all messages distributed by the
   list (including command responses to individual users), and on other
   messages where the message clearly applies to one distinct mailing
   list.  There MUST be no more than one of each header field present in
   any given message.

   These header fields MUST only be generated by mailing list managers,
   not by MUAs.

3.1.  List-Help

   The List-Help header field can direct the user to complete
   instructions for all other commands.  Typically, the URI specified
   would request the help file, perhaps incorporating an HTML form for
   list commands, for the list, and alternatively provide access to an
   instructive website.

   Syntax:

      uri-list = "<" URI ">" *("," [ FWS ] "<" URI ">")

      ; whereas <URI> is defined in RFC 3986 and <FWS> and




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      ; <CFWS> in RFC 5322

      ; CRLF is the carriage return/line feed pair

      list-help = "List-Help:" [ CFWS ] uri-list [ CFWS ] CRLF

   Examples:



      List-Help:  <mailto:list-request@example.com?subject=help> (List
         Instructions)



      List-Help:  <mailto:list-request@example.com?body=info>



      List-Help:  <mailto:list-info@example.com> (Info about the list)



      List-Help:  <http://www.example.com/list/>,
         <mailto:list-info@example.com>



      List-Help:  <ftp://ftp.example.com/list.txt> (FTP),
         <mailto:list-request@example.com?subject=help>

3.2.  List-Unsubscribe

   The List-Unsubscribe header field describes the command to directly
   unsubscribe the user (removing them from the list).

   Syntax:

      list-unsubscribe = "List-Unsubscribe:" uri-list [ CFWS ] CRLF

   Examples:



      List-Unsubscribe:
         <mailto:list-request@example.com?subject=unsubscribe>





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      List-Unsubscribe:  (Use this command to get off the list)
         <mailto:list-request@example.com?body=unsubscribe%20list>



      List-Unsubscribe:  <mailto:list-remove@example.com>



      List-Unsubscribe:
         <http://www.example.com/list.cgi?cmd=unsub&lst=list>,
         <mailto:list-request@example.com?subject=unsubscribe>

3.3.  List-Subscribe

   The List-Subscribe header field describes the command to directly
   subscribe the user (request addition to the list).

   Syntax:

      list-subscribe = "List-Subscribe:" uri-list [ CFWS ] CRLF

   Examples:



      List-Subscribe:
         <mailto:list-request@example.com?subject=subscribe>



      List-Subscribe:  (Use this command to join the list)
         <mailto:list-request@example.com?body=subscribe%20list>



      List-Subscribe:  <mailto:list-add@example.com>



      List-Subscribe:
         <http://www.example.com/list.cgi?cmd=sub&lst=list>,
         <mailto:list-request@example.com?body=subscribe%20list>






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3.4.  List-Post

   The List-Post header field describes the method for posting to the
   mailing list.  This is typically the email address of the mailing
   list.  It can also be the email address of a moderator, or
   potentially some other form of submission.  For the special case of a
   mailing list that does not allow posting (e.g., an announcements
   list), the List-Post field may contain the special value "NO".

   Syntax:

      list-post = "List-Post:" uri-list/"NO" [ CFWS ] CRLF

   Examples:



      List-Post:  <mailto:list@example.com>



      List-Post:  <mailto:list-moderator@example.com> (Postings are
         Moderated)



      List-Post:
         <mailto:list-moderator@example.com?subject=list%20posting>



      List-Post:  NO (posting not allowed on this list)

3.5.  List-Owner

   The List-Owner header field identifies the path to contact a human
   administrator for the mailing list.  The URI may contain the email
   address of an administrator for the mailing list, the mail system
   administrator, or any other person who can handle user contact for
   the mailing list.

   Syntax:

      list-owner = "List-Owner:" uri-list [ CFWS ] CRLF

   Examples:





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      List-Owner:  <mailto:list-admin@example.com> (Contact Person for
         Help)



      List-Owner:  <mailto:grant@example.com> (Grant Neufeld)



      List-Owner:  <mailto:josh@example.com?Subject=list>

3.6.  List-Archive

   The List-Archive header field describes how to access archives for
   the mailing list.

   Syntax:

      list-archive = "List-Archive:" uri-list [ CFWS ] CRLF

   Examples:



      List-Archive:
         <mailto:list-request@example.com?subject=index%20list>



      List-Archive:  <ftp://ftp.example.com/pub/list/archive/>



      List-Archive:  <http://www.example.com/list/archive/> (Web
         Archive)



      List-Archive:  <imap://archive.example.com/list>

   The Archive-At header field [RFC5064] provides a pointer to an
   archived form of a single message.







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3.7.  List-Sequence

   The List-Sequence header field provides a standard location for
   identifying the sequence position of an individual message for a
   mailing list [I-D.moonesamy-rfc2919bis].

3.8.  List-Id

   The List-Id header field provides an identifier for an e-mail
   distribution list [I-D.moonesamy-rfc2919bis].


4.  Supporting Nested Lists

   A mailing list that is a sublist for another mailing list in a nested
   mailing list hierarchy will need to modify some of the List- header
   fields, while leaving others as the parent list set them.

   Sublists SHOULD remove the parent list's List-Help, List-Subscribe,
   List-Unsubscribe and List-Owner header fields, and SHOULD insert
   their own versions of those header fields.

   If the sublist provides its own archive, it SHOULD replace the List-
   Archive header field with its own.  Otherwise, it MUST leave the
   List-Archive header field untouched.

   Dependant on how postings to the mailing list are handled, the
   sublist MAY replace the List-Post field.  The appropriateness of
   whether to replace List-Post is left to the determination of the
   individual list administrators.  If the intention is that postings
   should be distributed to all members of the primary mailing list,
   List-Post should not be changed by a sublist in such a way that
   postings will be distributed only to members of the sublist.


5.  Security Considerations

   There are very few new security concerns generated with this
   proposal.  Message headers fields are an existing standard, designed
   to easily accommodate new types.  There may be concern with multiple
   header fields being inserted or headers fields being forged, but
   these are problems inherent in Internet mail, not specific to this
   specification.

   Mailing list managers should not allow any user-originated list
   header fields to pass through to the mailing lists, lest they confuse
   the user and have the potential to create security problems.




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   On the client side, there may be some concern with posts or commands
   being sent in error.  It is required that the user have a chance to
   confirm any action before it is executed.  In the case of "mailto",
   it may be appropriate to create the correctly formatted message
   without sending it, allowing the user to see exactly what is
   happening and giving the user the opportunity to approve or discard
   the message before it is sent.

   All security considerations for the use of URIs [RFC3986] apply
   equally to this specification.  Mail User Agents should not process
   list header field URIs which could compromise the security of the
   user's system.  This includes the "file://" URI type which could
   potentially be used to trigger the execution of a local application
   on some user systems.


6.  IANA Considerations

   The List-Archive, List-Help, List-Owner, List-Post, List-Subscribe,
   and List-Unsubscribe references in the Permanent Message Header Field
   Names registry should be updated to point to this document.


7.  Acknowledgements

   The numerous participants of the List-Header, ListMom-Talk, List-
   Managers and MIDA-Mail mailing lists contributed much to the
   formation and structure of RFC 2369 with Keith Moore and Christopher
   Allen providing guidance on the standards process.

   We would like to thank the the following people for their
   contributions: Mykyta Yevstifeye, Murray S. Kucherawy and John
   Levine.


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.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, January 2005.

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



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

   [RFC6068]  Duerst, M., Masinter, L., and J. Zawinski, "The 'mailto'
              URI Scheme", RFC 6068, October 2010.

8.2.  Informative References

   [I-D.moonesamy-rfc2919bis]
              Moonesamy, S., "List-Id: A Structured Field and Namespace
              for the Identification of Mailing Lists",
              draft-moonesamy-rfc2919bis-02 (work in progress),
              January 2012.

   [RFC2142]  Crocker, D., "MAILBOX NAMES FOR COMMON SERVICES, ROLES AND
              FUNCTIONS", RFC 2142, May 1997.

   [RFC2369]  Neufeld, G. and J. Baer, "The Use of URLs as Meta-Syntax
              for Core Mail List Commands and their Transport through
              Message Header Fields", RFC 2369, July 1998.

   [RFC5064]  Duerst, M., "The Archived-At Message Header Field",
              RFC 5064, December 2007.


Appendix A.  Implementation

   RFC 2369 contains a discussion about the design decisions for List-
   header fields.


Appendix B.  Changes from RFC 2369

   This appendix contains a list of changes between this document and
   RFC 2369.

   o  URL changed to URI

   o  Replaced MTAs with mailing list managers in the sentence: "MTAs
      generating the header fields SHOULD".

   o  Replaced MTAs with mailing list managers in the sentence: "MTAs
      MUST NOT insert whitespace within the brackets" in Section 2

   o  In Section 2, client application SHOULD ignore whitespace within
      brackets





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   o  Updated references

   o  Added informative reference to RFC 5064

   o  Editorial changes

   o  Removed Background Discussion


Appendix C.  Change Log

   [RFC-Editor: please remove this section]

C.1.  Changes between between version -02 and version -03

   o  Added Grant Neufeld as co-author

   o  Added Joshua Baer as co-author

   o  Move List-Sequence header field definition to I-D.moonesamy-
      rfc2919bis

C.2.  Changes between between version -01 and version -02

   o  Added ABNF and reference to RFC 5234

   o  Removed text about postmaster in List-Owner Section

   o  Removed User Interface guidelines from Appendix B

   o  Removed SHOULD include a "mailto" based command in Section 3

   o  Modified the text to first paragraph of Section 3.1

C.3.  Changes between between version -00 and version -01

   o  Added List-Sequence header field

   o  Added informative reference to I-D.moonesamy-rfc2919bis












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Authors' Addresses

   S. Moonesamy (editor)
   76, Ylang Ylang Avenue
   Quatre Bornes
   Mauritius

   Email: sm+ietf@elandsys.com


   Grant Neufeld
   Calgary, Alberta
   Canada

   Email: grant@grantneufeld.ca


   Joshua Baer
   Austin, Texas
   USA

   Email: ietf@joshuabaer.com
   URI:   http://joshuabaer.com/




























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