5.0799 Internet Mail Extensions (1/101)

Elaine Brennan & Allen Renear (EDITORS@BROWNVM.BITNET)
Mon, 30 Mar 1992 16:02:51 EST

Humanist Discussion Group, Vol. 5, No. 0799. Monday, 30 Mar 1992.

Date: Sun, 29 Mar 92 12:08:45 EST
From: david j reimer f <dreimer4@mach1.wlu.ca>
Subject: MIME

Given the interest of HUMANISTs in subjects like Unicode and the
ISO10646 discussions, the following might also be of interest.

David Reimer
Wilfrid Laurier University

Date: Sun, 29 Mar 1992 10:38:46 -0500
Sender: mamut!unix-listserv@stormking.com
Version: 5.41 -- Copyright (c) 1991/92, Anastasios Kotsikonas
From: mamut!nestey@copper.Denver.Colorado.EDU (Nathan F. Estey)
Subject: MIME


MIME (Multipurpose Internet Mail Extensions):

Mechanisms for Specifying and Describing
the Format of Internet Message Bodies

Nathaniel Borenstein, Bellcore
Ned Freed, Innosoft
February, 1992

Status of this Document

This draft document will be submitted to the RFC editor as a
Proposed Standard protocol specification. Distribution of
this document is unlimited. Please send comments to
Nathaniel Borenstein <nsb@bellcore.com> or Ned Freed

Experimentation with the mechanisms described in this
document is encouraged. It is anticipated that such
experimentation will take place during the first half of
1992, after which this document will be revised and
submitted as a Draft Standard.


RFC 822 defines a message representation protocol which
specifies considerable detail about message headers, but
which leaves the message content, or message body, as flat
ASCII text. This document redefines the format of message
bodies to allow multi-part textual and non-textual message
bodies to be represented and exchanged without loss of
information. This is based on earlier work documented in
RFC 934 and RFC 1049, but extends and revises that work.
Because RFC 822 said so little about message bodies, this
document is largely orthogonal to (rather than a revision
of) RFC 822.

In particular, this document is designed to provide
facilities to include multiple objects in a single message,
to represent body text in character sets other than US-
ASCII, to represent formatted multi-font text messages, to
represent non-textual material such as images and audio
fragments, and generally to facilitate later extensions
defining new types of Internet mail for use by cooperating
mail agents.

INTERNET MIME: Multipurpose Internet Mail Extensions 3

1 Introduction

Since its publication in 1982, RFC 822 [RFC-822] has defined
the standard format of textual mail messages on the
Internet. Its success has been such that the RFC 822 format
has been adopted, wholly or partially, well beyond the
confines of the Internet and the Internet SMTP transport
defined by RFC 821 [RFC-821]. As the format has seen wider
use, a number of limitations have proven increasingly
restrictive for the user community.

RFC 822 was intended to specify a format for text messages.
As such, non-text messages, such as multimedia messages that
might include audio or images, are simply not mentioned.
Even in the case of text, however, RFC 822 is inadequate for
the needs of mail users whose languages require the use of
character sets richer than US ASCII [US-ASCII]. For mail
containing audio, video, Asian language text, or even text
in most European languages, RFC 822 does not specify enough
to provide interoperability.

One of the notable limitations of RFC 821/822 based mail
systems is the fact that they limit the contents of
electronic mail messages to relatively short lines of
seven-bit ASCII. This forces users to convert any non-
textual data that they may wish to send into seven-bit bytes
representable as printable ASCII characters before invoking
a local mail UA (User Agent, a program with which human
users send and receive mail). Examples of such encodings
currently used in the Internet include pure hexadecimal,
uuencode, the 3-in-4 base 64 scheme specified in RFC 1113,
the Andrew Toolkit Representation [ATK], and many others.

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