RFC 1524 (rfc1524) - Page 1 of 12
A User Agent Configuration Mechanism For Multimedia Mail Format Information
Alternative Format: Original Text Document
Network Working Group N. Borenstein
Request for Comments: 1524 Bellcore
Category: Informational September 1993
A User Agent Configuration Mechanism
For Multimedia Mail Format Information
Status of This Memo
This memo provides information for the Internet community. It does
not specify an Internet standard. Distribution of this memo is
unlimited.
Abstract
This memo suggests a file format to be used to inform multiple mail
reading user agent programs about the locally-installed facilities
for handling mail in various formats. The mechanism is explicitly
designed to work with mail systems based Internet mail as defined by
RFC's 821 (STD 10), 822 (STD 11), 934, 1049 (STD 11), 1113, and the
Multipurpose Internet Mail Extensions, known as MIME. However, with
some extensions it could probably be made to work for X.400-based
mail systems as well. The format and mechanism are proposed in a
manner that is generally operating-system independent. However,
certain implementation details will inevitably reflect operating
system differences, some of which will have to be handled in a
uniform manner for each operating system. This memo makes such
situations explicit, and, in an appendix, suggests a standard
behavior under the UNIX operating system.
Introduction
The electronic mail world is in the midst of a transition from
single-part text-only mail to multi-part, multi-media mail. In
support of this transition, various extensions to RFC 821 and RFC 822
have been proposed and/or adopted, notably including MIME [RFC-1521].
Various parties have demonstrated extremely high-functionality
multimedia mail, but the problem of mail interchange between
different user agents has been severe. In general, only text
messages have been shared between user agents that were not
explicitly designed to work together. This limitation is not
compatible with a smooth transition to a multi-media mail world.
One approach to this transition is to modify diverse sets of mail
reading user agents so that, when they need to display mail of an
unfamiliar (non-text) type, they consult an external file for
information on how to display that file. That file might say, for
Borenstein
