X400: Definition of ADMD

The information in this article applies to:

• Microsoft Mail Gateway to X.400, version 3.0

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

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.