MIME - X.400 Enhanced Relay - MIXER
MIXER is about gatewaying between MIME and X.400 email.
Nobody's done anything to it recently, so it's a stable spec, but
complex enough to be an useful example.
From the announce:
MIXER is an update to RFC 1327 which specifies mappings between
RFC822/SMTP and X.400 mail.
This update corrects several errors in RFC 1327, includes supprot for
MIME as well as Internet standards-track delivery status notifications
and SMTP extensions to request delivery reports, and defines a
standard notation for representation of address mapping and routing
information between X.400 and Internet Mail.
2005-10-21