Platform SDK: Exchange Server

X

X.400
An international message-handling standard for connecting e-mail networks and for connecting users to e-mail networks. X.400 is published by the X.400 Application Programming Interface Association (XAPIA). MAPI applications are fully interoperable with X.400 messaging applications.
X.500
An international message-handling standard for directory services, published by the International Telegraph and Telephone Consultative Committee (CCITT) standards body.