The Defense Message System (DMS) is a secure X.400-based e-mail system developed by the United States government in conjunction with industry partners to ensure safety for critical operations. Essentially an enhanced version of various commercial e-mail products, DMS was developed for the United States Department of Defense (DoD). DMS has replaced AUTODIN (automated digital network), the previous official DoD e-mail system as well as 45 separate e-mail systems that functioned within the DoD.
At the client level, DMS looks like a typical e-mail application and is designed to feature familiar user-friendly functionality, such as global X.500 Directory Service, and transmission support for digital files of any type and size. Security and delivery assurance mechanisms are approved by the National Security Agency (NSA) for information classified at all levels, up to and including those designated as top secret. Because sending message attachments between the unclassified and secret domains (known, respectively, as NIPRNET and SIPRNET) requires protection against leakage of classified information, DMS policies require that all organizational messages be signed and encrypted with Class IV Public Key Infrastructure (PKI) protection through Fortezza, NSA's trademarked security products suite. Originally policies permitted organizational message attachments to be sent only from a low security domain to a high security domain, but security mechanisms (both technological and policy-based) are now in place to allow the information to flow in either direction.
DMS was designed to incorporate components from a variety of leading hardware and software vendors and to leverage the best current and emerging messaging technologies within the Defense Information Infrastructure (DII, a worldwide connectivity transport infrastructure). The DMS development program began in response to Joint Staff requirements for an integrated messaging service that could be accessed from any DoD location in the world, as well as by designated government users or contractors. DMS has been recommended to become the standard messaging system throughout the United States government.