23.2 MULTIPURPOSE INTERNET MAIL EXTENSION (MIME)

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MIME is defined in RFC 1521 and 1522. The specifications include:

Five new message header fields that provide information about the body of the message.
A number of content formats to support multimedia mail.

The five header fields are:

MIME Version 1.0 (conforms to RFC 1521 and 1522).
Content type that describes data contained in the body.
Content transfer encoding that indicates the type of transformation that has been used to represent the body of the message.
Content ID to uniquely identify MIME content types.
Content description: plain text description of object, such as audio, text, or video clip.

Some of the MIME content types are listed here.

Type	Subtype	Description
Text	Plain
Multipart	Mixed	To be presented to the user in the order they appear.
	Parallel	No order is required.
	Alternative	Alternative version, best to be displayed.
	Digest	Similar to mixed, but RFC 822.
Message	RFC822
Partial	Fragment	Large mails.
	External body	Pointer to object
Image	JPEG
	GIF
Video	MPEG
Audio	Basic	8-bit at 8kHz
Application	PostScript
	Octet stream	Binary data with 8-bit types.

An example MIME header looks like this:

 From: kvkk.prasad@ieee.org To: kvravi@ece.nus.sg Sub: demo MIME Version 1.0 Content type: multipart/mixed Content type: video/MPEG

MIME is an extension to SMTP to provide multimedia message content to e-mails. In addition to plain text, images, executable files, audio, and video clips can be attached to the e-mail. MIME is defined in RFCs 1521 and 1522.

Hence, MIME is an extension to the SMTP to provide multimedia support in the message of the mail using the various MIME types.

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