Pre-Defined MIME Types

Each part of a multi-media message identifies what type of information is carried in the message part. For example, a message part containing audio data might have either type audio/basic or type audio/x-next. Both are audio types; the subtypes are basic and x-next.

An entire MIME message—as opposed to an individual part of a multipart message—can also have a type. For example, a message might have the type text/plain, and consist entirely of plain text. A MIME message containing parts of different types has the umbrella type multipart/mixed.

Here are brief summaries of the pre-defined types and subtypes in MIME 1.0. Except where noted, each of these types may be specified in an mhn directive in a message draft, preceded by a hash mark (#) at the start of a line.


\begin{comdesc}
% latex2html id marker 922\item[application/octet-stream] is f...
... into
a draft, the video data is encoded in MIME's base64 format.
\end{comdesc}

There may be other registered types and subtypes down the road. MIME also allows arbitrary subtypes whose names are prefixed with ``x-'', but anything else is reserved for registered types.

The MIME specification, RFC 1341, contains more detailed explanations of required or optional attributes to be used with particular types. Type names used with mhn correspond to those used in the MIME specification.

Base64 is a textual encoding used in MIME messages. Base64 is designed to permit data to survive the most common sorts of transformations that mail gateways apply to message bodies, such as breaking long lines of text into multiple lines. Base64 is similar in concept to the encoding used by uuencode, except that uuencoded data doesn't always survive intact when transported through certain mail gateways.