http://www.rfc-editor.org/rfc/rfc2049.txt
RFC 2049: Multipurpose Internet Mail Extensions (MIME) Part Five: Conformance Criteria and Examples, N. Freed, N. Borenstein1996-11-01T23:00:00-00:00This set of documents, collectively called the Multipurpose Internet Mail Extensions, or MIME, redefines the format of messages. This fifth and final document describes MIME conformance criteria as well as providing some illustrative examples of MIME message formats, acknowledgements, and the bibliography. [STANDARDS-TRACK]