Note: Many topics at this site are reduced versions of the text in "The Encyclopedia of Networking and Telecommunications." Search results will not be as extensive as a search of the book's CD-ROM.

Electronic mail systems have specific addressing schemes that identify users and resources on the network. These addressing schemes identify the area or domain and the specific node within the area or domain in which a user or resource exists .

The Internet, a global network of users, employs a hierarchical naming scheme as part of its DNS (Domain Name System). An address for a user attached to a local area network or a network attached to the organization's e-mail hub might be the following, which addresses John Doe (jdoe) at the library, University of California, Berkeley. The last portion, "edu," is the Internet top-level domain name indicating an educational institution.

Two other standards should be mentioned. The X.400 specifications are a set of e-mail communications standards developed by the CCITT (Consultive Committee for International Telegraphy), now the ITU-T (International Telecommunication Union-Telecommunications Sector). Basically, X.400 set some precedents for e-mail, but never became as popular as Internet mail.

X.500 is a directory services standard that provides so-called white pages naming services for enterprise networks. While X.500 never became a popular standard for use in electronic mail addressing, a subset of X.500 standards has been implemented in LDAP (Lightweight Directory Access Protocol). White page services are important because they help users locate other users for a variety of activities, including addressing electronic mail to them. Note that with LDAP, the predominant addressing scheme is the Internet address.

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