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The set of ITU-T communications standards covering electronic mail services provided by data networks. X.400 was widely used in Europe and Canada.

X.400 addresses tend to be much longer than RFC 822 ones. They consist of a set of bindings for country (c), administrative domain (a), primary management domain (p), surname (s), given name (g).

For example, the X.400 address,

c=gb;a=attmail;p=Universal Export;s=Bond;g=James;

might be equivalent to RFC 822


This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)


An OSI and ITU standard messaging protocol. It is an application layer protocol (layer 7 in the OSI model). X.400 has been defined to run over various network transports including Ethernet, X.25, TCP/IP and dial-up lines. See messaging protocol, XAPIA and CMC. Following is the format of an X.400 address:

/c=  /admd=  /prmd=  /o=  /s=  /g=X.400Code     Purpose

 /c=      country

 /admd=   administrative management domain
           (public email service)

 /prmd=   private management domain
           (in-house email)

 /o=      organization

 /s=      surname

 /g=      given name
Copyright © 1981-2019 by The Computer Language Company Inc. All Rights reserved. THIS DEFINITION IS FOR PERSONAL USE ONLY. All other reproduction is strictly prohibited without permission from the publisher.
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