MIME Hierarchies of Body Parts

A Multipurpose Internet Mail Extensions (MIME)-formatted message is divided into a hierarchy of body parts. Multipart body parts define the relationships between descendant body parts, and content body parts contain the actual content of the message. The illustration below represents a typical MIME hierarchy for a message that contains the following content:

• Alternative versions of the message, in US-ASCII plain text and HTML

• A related image used to render the HTML content

• A Microsoft® Word attachment

Content body parts are displayed in a shaded box labeled Content. Multipart body parts act as structural nodes in the hierarchy and define the relationships among the descendant content body parts.

Multipart/Mixed Structure

The format of a MIME header is specified by RFC 2045. For a complete description of the MIME message format, see RFC 2045, RFC 2046, RFC 2047, RFC 2048, and RFC 2049.