Updated: 11/13/2018 by Computer Hope

Originally published in 1984 by CCITT and later re-written in 1988 jointly by ISO and CCITT, X.400 is a network communications standard. It conforms to layer 7 of the OSI and is a standard used for transporting e-mail messages. X.400 is an alternative standard to the commonly used SMTP and includes support for several transport connections including Ethernet, TCP/IP, and dial-up.

Example of SMTP e-mail address

[email protected]

Example of a X.400 e-mail address

G=support; O=computerhope.com

Where G is the given name.

CCITT, E-mail, E-mail terms, ISO, OSI