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Versions: 00                                                            
Network Working Group                                          C. Newman
Internet Draft: Reply-To-Meaning Proposal                       Innosoft
Document: draft-ietf-drums-replyto-meaning-00.txt          November 1997


                       Reply-To-Meaning Proposal


Status of this memo

     This document is an Internet-Draft.  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-Drafts.

     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."

     To view the entire list of current Internet-Drafts, please check
     the "1id-abstracts.txt" listing contained in the Internet-Drafts
     Shadow Directories on ftp.is.co.za (Africa), ftp.nordu.net
     (Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
     Coast), or ftp.isi.edu (US West Coast).


Introduction

     This is a candidate proposal for one way which the problems with
     the reply-to header in email could be resolved.  Under no
     circumstances should this be implemented as it is only a candidate
     for a solution and no decision has yet been made.  This proposal
     distinguishes the different incompatible uses of the Reply-To
     header with a new Reply-To-Meaning header.  This has the advantage
     of being relatively simple, not invalidating most current practices
     and allowing mail user agents to present more predictable user
     interfaces.


1. Conventions Used in this Document

     The key words "REQUIRED", "MUST", "MUST NOT", "SHOULD", "SHOULD
     NOT", and "MAY" in this document are to be interpreted as described
     in "Key words for use in RFCs to Indicate Requirement Levels"
     [KEYWORDS].




Newman                                                          [Page 1]


Internet Draft         Reply-To-Meaning Proposal           November 1997


2. Reply-To Current Practice

     The Reply-To header is currently used for the following purposes:

     (1) The author/sender can suggest a complete list of addresses
     which should receive any reply (e.g., a review committee).

     (2) The author/sender can recommend an address or addresses to use
     instead of the "from" address for replies.

     (3) The author/sender can post to multiple mailing lists and
     suggest group replies go to only one of them.

     (4) When the author/sender is subscribed to a mailing list, he can
     suggest that he doesn't want two copies of group replies to
     messages he posts to the list.

     (5) A mailing list can suggest that the list is a discussion list
     and replies should be sent just to the list by default.

     Many current MUAs have undesirable results with one or more of
     these uses.  However, if the MUA knew the intent when the reply-to
     header was added, the undesirable results can be eliminated.

     Alternative proposals to this one have suggested that the meaning
     of Reply-To be restricted to (1), (2) or (3) and that additional
     headers would be added for any of the other uses deemed important.


3. Reply-To-Meaning Header

     The Reply-To-Meaning header is used to indicate the intent when the
     Reply-To header was added.  It has five values: "any", "private",
     "group", "non-list" or "list."


     any
          The "any" meaning indicates that the author/sender added the
          reply-to header as a suggested target for any reply (e.g., use
          1 above).

     private
          The "private" meaning indicates that the author/sender added
          to Reply-To header as an address for private replies to use
          instead of the "From" header (e.g., use 2 above).

     group
          The "group" meaning indicates that the author/sender added the



Newman                                                          [Page 2]


Internet Draft         Reply-To-Meaning Proposal           November 1997


          Reply-To header as a complete list of addresses where group
          replies should be sent (e.g., use 3 and/or 4 above).

     non-list
          The "non-list" meaning simply indicates that the author/sender
          added the reply-to header (e.g., any one of 1-4 above).

     list
          The "list" meaning indicates that the Reply-To header was
          added by a mailing list (e.g., use 5 above).


     The formal syntax using ABNF from message format standard:

     reply-to-meaning-header = "Reply-To-Meaning:" 1*FWS meaning-keyword

     meaning-keyword = "any" / "private" / "group" / "non-list" / "list"
                       / extension-token

     Unknown extension-tokens are treated as equivalent to no Reply-To-
     Meaning header.  Meaning keywords are interpreted in a
     case-insensitive fashion.

4. Examples

     Here are a series of examples of various uses:

         From: Chris Newman <chris.newman@innosoft.com>
         To: DRUMS mailing list <drums@cs.utk.edu>
         Subject: I'll collect straw-poll responses
         Reply-To: Chris Newman <chris.newman+straw-poll@innosoft.com>
         Reply-To-Meaning: any

     In this mailing list posting, the author has asked that all replies
     go to his straw-poll address.

         From: Chris Newman <chris.newman@innosoft.com>
         To: DRUMS mailing list <drums@cs.utk.edu>
         Reply-To: Chris's DRUMS inbox <chris.newman+drums@innosoft.com>
         Reply-To-Meaning: private

     This author has a special address for private replies to his
     postings on this list.  This might also be used by a someone with a
     secretary to review incoming responses.

         From: Chris Newman <chris.newman@innosoft.com>
         To: DRUMS mailing list <drums@cs.utk.edu>
         Reply-To: DRUMS mailing list <drums@cs.utk.edu>



Newman                                                          [Page 3]


Internet Draft         Reply-To-Meaning Proposal           November 1997


         Reply-To-Meaning: group

     This author doesn't want private copies of replies sent to the
     list.

         From: Chris Newman <chris.newman@innosoft.com>
         To: DRUMS mailing list <drums@cs.utk.edu>
         Reply-To: DRUMS mailing list <drums@cs.utk.edu>
         Reply-To-Meaning: non-list

     This indicates that the author explicitly added the Reply-To header
     and the mailing list didn't change it.  Although meaning (2) can't
     be distinguished from meanings (1), (3) or (4), this does give
     assurance that the author will see replies if the Reply-To header
     is used without the From header.

         From: Chris Newman <chris.newman@innosoft.com>
         To: DRUMS mailing list <drums@cs.utk.edu>
         Reply-To: DRUMS mailing list <drums@cs.utk.edu>
         Reply-To-Meaning: list

     This indicates that the list is a discussion list and it added the
     Reply-To header to direct generic replies to the list.  There is no
     assurance that the author is subscribed to the list.  In addition,
     if the author included additional lists or people in a CC header,
     they probably won't see replies directed only to the Reply-To
     header.


5. Interpretation in Common Reply Functions

     Many user agents provide more than one function to construct a
     default set of target addresses for replies.  This section suggests
     how Reply-To-Meaning can be interpreted by certain common reply
     functions:


     Private Reply
          A private reply is intended for the author(s) or the
          delegate(s) of the author(s).  When there is no Reply-To
          header, or the Reply-To-Meaning is "group" or "list" then the
          From header is used as the default set of target addresses for
          replies.  When Reply-To-Meaning is "private", then the Reply-
          To header is used instead of the From header.  If there is no
          Reply-To-Meaning, or Reply-To-Meaning is "any" or "non-list"
          then the MUA can offer the user a choice between using the
          Reply-To or "From" header.




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Internet Draft         Reply-To-Meaning Proposal           November 1997


          NOTE: if a Reply-To header was constructed with intent (1) or
          (3)-(5), and was used without warning in a private reply, then
          the reply could be directed to more recipients than the user
          intended and cause serious embarassment or other undesirable
          consequences.


     Group Reply (also known as Reply All)
          A group reply is intended for all authors and recipients of
          the original message.  When there is no Reply-To header, it is
          constructed by using the contents of the original From, To and
          CC header as the default set of reply targets (with duplicates
          and possibly the replying user's address removed).  When
          Reply-To-Meaning is "any" or "group" the Reply-To address is
          used as the complete set of reply targets.  When Reply-To-
          Meaning is "private" or "non-list", the Reply-To, To and CC
          addresses are used as the default set of targets.  Otherwise,
          Reply-To, To, CC and From are all used as the default set of
          targets.

          NOTE: This can result in undesired duplicate copies of a reply
          when a list address is included which the original author was
          subscribed to and Reply-To-Meaning is not added.  However,
          this definition assumes duplicate copies are less harmful than
          risking the omission of the original author.  With the
          opposite assumption, if Reply-To-Meaning was "list" or absent
          only the Reply-To, To and CC headers would be used.


     Generic Reply / Gateway
          A generic reply is simply a desire to reply to the set of
          recipients most likely to want the reply.  It does not specify
          a preference for a "private" or "group" reply.  This is also
          the set of addresses that gateways are forced to convey when
          the target mail environment has a single reply-target address
          list.  This is defined as the Reply-To header, if present, and
          the From header otherwise.  User agents which offer this
          function should draw attention to the Reply-To header when
          it's present.  Reply-To-Meaning has no impact on this
          function.


6. Mailing List Rules

     When a mailing list receives a message it MUST NOT alter an
     existing Reply-To header.  If there is a Reply-To header and no
     Reply-To-Meaning header, the list SHOULD add a "Reply-To-Meaning:
     non-list" header.



Newman                                                          [Page 5]


Internet Draft         Reply-To-Meaning Proposal           November 1997


     Mailing lists SHOULD NOT add a Reply-To header when one is not
     present.  However, if they do they MUST also add "Reply-To-Meaning:
     list."  In the short term it is particularly undesirable to do
     this, as it can cause problems for user agents which don't
     understand the Reply-To-Meaning header.  Such user agents may make
     it difficult to construct private replies.  In addition, if a
     message is posted to several lists, generic replies and some older
     user agents may fragment the conversation to a single list.


7. Pro/Con Analysis

     Pros:

     * This is a fairly simple proposal

     * This does not invalidate most current practices, which minimizes
     deployment problems.

     * This won't cause problems for legacy gateways which will never be
     upgraded.

     Cons:

     * This is an ugly design because it leaves Reply-To overloaded.

     * Legacy mailing lists which change existing reply-to headers will
     really mess things up.

     * This opens up the possibility of permitting lists to add Reply-To
     headers which could cause short term problems as discussed in
     section 6.

     * There is no way to redirect private replies to a non-author and
     group replies to a different target in the same message.


8. Security Considerations

     There are a number of cases where a private reply could be
     misdirected to a large group of people.  Although this proposal
     reduces the chances of this happening, it remains important for
     MUAs to draw attention to Reply-To headers and reply targets in
     most situations.


9. Open Issues with this Proposal




Newman                                                          [Page 6]


Internet Draft         Reply-To-Meaning Proposal           November 1997


     The "any" meaning will force current user agents to change their
     interfaces for private replies when "any" is present.  This will
     probably be controversial.

     The severity of the pros and cons is probably controversial.


10. References

     [IMAIL] Crocker, D., "Standard for the Format of Arpa Internet Text
     Messages", RFC 822, University of Delaware, August 1982.

          <ftp://ds.internic.net/rfc/rfc822.txt>

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

         <ftp://ds.internic.net/rfc/rfc2119.txt>


11. Author's Address

     Chris Newman
     Innosoft International, Inc.
     1050 Lakes Drive
     West Covina, CA 91790 USA

     Email: chris.newman@innosoft.com























Newman                                                          [Page 7]