Here is the change list for the latest draft of the document:
MAJOR CHANGES SINCE OCTOBER DRAFT OF RFC-XXXX
Renamed Body-Version to MIME-Version. (MIME = Multipurpose Internet
Mail Extensions.) The Content-Type header field is no longer required
-- MIME-Version suffices for plain US-ASCII text.
Regularized the syntax to attribute=value for parameters. (The
multipart parameter is now named "boundary". Character sets are named
by "charset" parameters. Message/partial parameters are id, number, and
total.) There are now NO default subtypes. This made the collected
grammar appendix MUCH smaller.
Merged text-plus into text. Defined text/plain. Made "octet-stream" the
only subtype of binary. Added "padding" parameter to indicate number of
bits padded in application/octet-stream type.
New Audio/basic format
Cleaned up external-reference and moved it to message/externalbody
Clarified message/partial, added example.
Added header & footer to richtext.
Quoted printable changes: chagned : to = as quoting character. Got rid
of the old rule 2 (== for "="), so that the equal sign must now be
expressed as "=3D".
In base64, got rid of portable newlines facility
Multipart changes: Liberalized requirements for multipart/alternative,
and reversed the order. Changed encapsulation boundary to include
leading CRLF. Added EBCDIC-invariants to the acceptable boundary
characters. Check out new prose & BNF!
Added "?", ".", and "=" to tspecials. Changed several uses of "atom" to
"token" to tighten up the BNF.
Moved PostScript to application, detailing security considerations as well.
New prose for ISO-2022-jp, ISO-10646, and MNEMONIC
Nuked old Appendix D (ASCII definition). Added new Appendix G, summary
of content-types. Is there more info that should go here?
Added requirement that embedded headers inside multipart & message types
must not be reordered or otherwise tampered with.
The following names should be internationalized, at least in the
PostScript version: Keld Jxrn Simonsen, Olle Jdrnefors, Patrik Fdlstrvm.
MAJOR CHANGES TO CONFIGURATION (MAILCAP) DOCUMENT
Much cleanup of syntactic and semantic ambiguities, particularly the
quoting convention.
In mailcap files, the "notes" field is now named & optional.
New fields for specifying "test=", "compose=", "composetyped=", and more.
New mailcap file syntax for passing parameters from the content-type
line to interpreter programs.