SUMMARY
ADMD is the abbreviation for ADministration Management Domain. This term
is defined by the CCITT X.400 standard which defines the basis for a
unified, world-wide, electronic mail (e-mail) network. The network
functions through the cooperation of independent operators of public and
private e-mail systems, each of whom manages a separate domain. No single
international authority, government, company, or other body assigns names
and addresses to the network.
X.400 defines a two-level domain structure. Level-1 domains are termed
ADMD and level-2 domains are termed PRMD (PRivate Management Domain).
As stated in section 7.3.3 of the F.400 standard:
In one country one or more ADMDs can exist. An ADMD is characterized
by its provision of relaying functions between other Management Domains
and the provision of Message Transfer Service for the applications
provided within the ADMD
A PRMD "is characterized by the provision of messaging functions" with
the domain (F.400, section 7.3.4).
Typically, a company or organization operates a PRMD to facilitate
communications within a local organization and uses an ADMD to serve
as the e-mail hub between sites, either within the same country or
internationally. If the PRMDs use the transfer services of different
ADMDs, or access mailboxes in the ADMDs, each ADMD must be linked.
This link could be direct or a relay through another ADMD.
The X.400 standard discusses administrations because CCITT is part of
the International Telecommunications Union (ITU), a United Nations
organization. CCITT groups governmental bodies (another name for
administrations). However, a number of private companies operate ADMDs
and the number of companies grows as the postal, telephone, and telegraph
(PTT) authorities are sold to private investors.