RFC 2369 (rfc2369) - Page 2 of 15

The Use of URLs as Meta-Syntax for Core Mail List Commands and their Transport through Message Header Fields

RFC 2369                  URLs as Meta-Syntax                  July 1998


1. Introduction

   This is a proposal for additional header fields to be added to email
   messages sent by email distribution lists. The content of each new
   field is typically a URL - usually mailto [RFC 2368] - which locates
   the relevant information or performs the command directly. MTAs
   generating the header fields SHOULD usually include a mailto based
   command, in addition to any other protocols used, in order to support
   users who do not have access to non-mail-based protocols.

   Implementing these fields will be optional. Significant functionality
   and convenience can be gained by including them, however. Many list
   managers, especially as the proposal first gains acceptance, MAY
   choose to implement only one or two of the fields.  The List-Help
   field is the most useful individual field since it provides an access
   point to detailed user support information, and accommodates almost
   all existing list managers command sets. The List-Subscribe and
   List-Unsubscribe fields are also very useful, but cannot describe
   some list manager syntaxes at this time (those which require variable
   substitution). See appendix A.5 for an explanation.

   The description of command syntax provided by the fields can be used
   by mail client applications to provide simplified and consistent user
   access to email distribution list functions. This could take the form
   of menu items, push buttons, or other user interface elements.  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
   fields, while at the same time avoiding the overloading of individual
   fields and keeping the syntax clear and simple.

   The use of these fields does not remove the requirement to support
   the -Request command address for mailing lists [RFC 2142].

2. The Command Syntax

   The list header fields are subject to the encoding and character
   restrictions for mail headers as described in [RFC 822]. Additionally,
   the URL content is further restricted to the set of URL safe
   characters [RFC 1738].

   The contents of the list header fields mostly consist of angle-
   bracket ('') enclosed URLs, with internal whitespace being
   ignored. MTAs MUST NOT insert whitespace within the brackets, but
   client applications should treat any whitespace, that might be
   inserted by poorly behaved MTAs, as characters to ignore.



Neufeld & Baer              Standards Track