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
Alternative Format: Original Text Document
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