MIME Hierarchies of Body Parts

In messages formatted in MIME, the body is subdivided into a hierarchy of nested body parts. The diagram below represents a typical MIME hierarchy for a message that contains the following content body parts:

• Alternative versions of the message in US-ASCII and HTML.
• A related image that renders the HTML content.
• A Microsoft Word attachment.

The body parts that hold content have a shaded box with the label content. The others are multipart body parts, act as structural nodes in the hierarchy, and define the relationships of the content body parts.

Multipart/Mixed Structure

The format of the 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.