RFC 1341 (rfc1341) - Page 2 of 77
MIME (Multipurpose Internet Mail Extensions): Mechanisms for Specifying and Describing the Format of Internet Message Bodies
Alternative Format: Original Text Document
RFC 1341MIME: Multipurpose Internet Mail ExtensionsJune 1992
This document describes several mechanisms that combine to
solve most of these problems without introducing any serious
incompatibilities with the existing world of RFC 822 mail.
In particular, it describes:
1. A MIME-Version header field, which uses a version number
to declare a message to be conformant with this
specification and allows mail processing agents to
distinguish between such messages and those generated
by older or non-conformant software, which is presumed
to lack such a field.
2. A Content-Type header field, generalized from RFC 1049
[RFC-1049], which can be used to specify the type and
subtype of data in the body of a message and to fully
specify the native representation (encoding) of such
data.
2.a. A "text" Content-Type value, which can be used to
represent textual information in a number of
character sets and formatted text description
languages in a standardized manner.
2.b. A "multipart" Content-Type value, which can be
used to combine several body parts, possibly of
differing types of data, into a single message.
2.c. An "application" Content-Type value, which can be
used to transmit application data or binary data,
and hence, among other uses, to implement an
electronic mail file transfer service.
2.d. A "message" Content-Type value, for encapsulating
a mail message.
2.e An "image" Content-Type value, for transmitting
still image (picture) data.
2.f. An "audio" Content-Type value, for transmitting
audio or voice data.
2.g. A "video" Content-Type value, for transmitting
video or moving image data, possibly with audio as
part of the composite video data format.
3. A Content-Transfer-Encoding header field, which can be
used to specify an auxiliary encoding that was applied
to the data in order to allow it to pass through mail
transport mechanisms which may have data or character
set limitations.
4. Two optional header fields that can be used to further
describe the data in a message body, the Content-ID and
Content-Description header fields.
Borenstein & Freed