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

From the thumper archive, there is:

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.
which came with it.