Post Office Protocol: Version 3: Extended service offerings
RFC 1082

Document Type RFC - Unknown (November 1988; No errata)
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Network Working Group                                            M. Rose
Request for Comments: 1082                                           TWG
                                                           November 1988

                    Post Office Protocol - Version 3
                       Extended Service Offerings

Status of This Memo

   This memo suggests a simple method for workstations to dynamically
   access mail from a discussion group server, as an extension to an
   earlier memo which dealt with dynamically accessing mail from a
   mailbox server using the Post Office Protocol -  Version 3 (POP3).
   This RFC specifies a proposed protocol for the Internet community,
   and requests discussion and suggestions for improvements.  All of the
   extensions described in this memo to the POP3 are OPTIONAL.
   Distribution of this memo is unlimited.

Introduction and Motivation

   It is assumed that the reader is familiar with RFC 1081 that
   discusses the Post Office Protocol - Version 3 (POP3) [RFC1081].
   This memo describes extensions to the POP3 which enhance the service
   it offers to clients.  This additional service permits a client host
   to access discussion group mail, which is often kept in a separate
   spool area, using the general POP3 facilities.

   The next section describes the evolution of discussion groups and the
   technologies currently used to implement them.  To summarize:

       o An exploder is used to map from a single address to
       a list of addresses which subscribe to the list, and redirects
       any subsequent error reports associated with the delivery of
       each message.  This has two primary advantages:
             - Subscribers need know only a single address
             - Responsible parties get the error reports and not
               the subscribers

Rose                                                            [Page 1]
RFC 1082                 POP3 Extended Service             November 1988

       o Typically, each subscription address is not a person's private
       maildrop, but a system-wide maildrop, which can be accessed
       by more than one user.  This has several advantages:
             - Only a single copy of each message need traverse the
               net for a given site (which may contain several local
               hosts).  This conserves bandwidth and cycles.
             - Only a single copy of each message need reside on each
               subscribing host.  This conserves disk space.
             - The private maildrop for each user is not cluttered
               with discussion group mail.

   Despite this optimization of resources, further economy can be
   achieved at sites with more than one host.  Typically, sites with
   more than one host either:

        1.  Replicate discussion group mail on each host.  This
        results in literally gigabytes of disk space committed to
        unnecessarily store redundant information.

        2.  Keep discussion group mail on one host and give all users a
        login on that host (in addition to any other logins they may
        have).  This is usually a gross inconvenience for users who
        work on other hosts, or a burden to users who are forced to
        work on that host.

   As discussed in [RFC1081], the problem of giving workstations dynamic
   access to mail from a mailbox server has been explored in great
   detail (originally there was [RFC918], this prompted the author to
   write [RFC1081], independently of this [RFC918] was upgraded to
   [RFC937]).  A natural solution to the problem outlined above is to
   keep discussion group mail on a mailbox server at each site and
   permit different hosts at that site to employ the POP3 to access
   discussion group mail.  If implemented properly, this avoids the
   problems of both strategies outlined above.

        ASIDE:     It might be noted that a good distributed filesystem
                   could also solve this problem.  Sadly, "good"
                   distributed filesystems, which do not suffer
                   unacceptable response time for interactive use, are
                   few and far between these days!

   Given this motivation, now let's consider discussion groups, both in
   general and from the point of view of a user agent.  Following this,
   extensions to the POP3 defined in [RFC1081] are presented.  Finally,
   some additional policy details are discussed along with some initial

Rose                                                            [Page 2]
RFC 1082                 POP3 Extended Service             November 1988

What's in a Discussion Group

   Since mailers and user agents first crawled out of the primordial
   ARPAnet, the value of discussion groups have been appreciated,
   (though their implementation has not always been well-understood).

   Described simply, a discussion group is composed of a number of
   subscribers with a common interest.  These subscribers post mail to a
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