MIME

MIME (MultiMedia Internet Mail Extensions) is a proposed standard for the exchange of mixed format information.

From the thumper archive, there is:

Overview
Internet Multimedia Mail with MIME: Emerging Standards for Interoperability. Paper accepted for ULPAA92.
Body Formats
MIME (Multipurpose Internet Mail Extensions): Mechanisms for Specifying and Describing the Format of Internet Message Bodies. Draft of RFC.
MIME Gateway
Implications of MIME for Internet Mail Gateways. Draft of RFC.
README
which came with it.