X.400, often referred to as Message Handling System (MHS ), is an e -mail system based on the OSI model and an alternative to Internet e -mail. The standard was published in 1984 by the CCITT (now ITU) and expanded in 1988. The ISO identifies the system in its standard ISO 10021, which is based on X.400 ( 1988), as Message Oriented Text Interchange System ( MOTIS ).

In Germany X.400 is often known under the old brand name Telebox400 the Federal Post Office. Meanwhile, the successor German Telekom referred to it as a business X.400. EDI systems often use X.400 for the transmission of data.

Access to the Message Store is done from X.400 ( 1988), in the X.419 P7 protocol defined by the user agent (UA) to the Message Store ( MS). The message exchange by means of a message transfer system (MTS ), which can consist of non- X.400 system of one or more message transfer agent (MTA) and gateways. The Telekom Germany GmbH provides for the transmission of messages to and a client that can transmit messages based on the protocol P7. This client software is called Work File for Windows ( all versions) and is now available in version 5.0. Likewise filework has a scripting interface, with which the program automatically delivers messages in both directions and processed accordingly.

The MTA is the central component for the message exchange with other X.400 systems. Using pre- configured routing information of the MTA decides based on the X.400 destination address on which way the messages are forwarded to the recipient. An X.400 address has a hierarchical structure and identifies the sender and receiver clearly.

Unlike Internet e- mail there is the global X.400 network only known by name domain owner and comprehensible ways in which the messages are moved through the network. For this reason, it is sometimes omitted in the use of X.400 to encrypt the message.

For the transmission of EDI messages, for example in the European food trade, X.400 is often used.

X.400 is next to AS2 one of the most common forms of communication that are used in professional electronic data exchange. Whether a company uses X.400 or AS2, decides on how the company weighted certain operating costs and which EDI infrastructure it owns. With AS2 can be saved with the provider for the X.400 service fees. This savings is offset by a higher cost in-house to manage the renewal regularly partner individual certificates and operation of uninterruptible own EDI system. X.400 is the X.400 provider between two EDI systems so that both partners do not communicate directly. Likewise, Compound tests for new partner connection or the troubleshoot connectivity problems in X.400 are simpler, because it is abstracted from direct communication partner.

Within the framework of the German research network on which most academic institutions were involved, an X.400 -compliant product called EAN was offered from 1985. According to the needs of academic life there was in the composite gateways to BITNET or EARN and to the Internet. Due to the global dominance of the TCP / IP-based applications, the product became obsolete in the early 1990s.

Norms and Standards

The following recommendations were developed under the supervision of CCITT and ratified by the ITU (CCITT ). They form the standard X.400 ( 1988), which expands the standard X.400 ( 1984).

  • Recommendation X.400, Message Handling: System and Service Overview, ITU (CCITT ) Blue Book, Fascicle VIII.7, International Telecommunications Union, 1988 ( see ISO 10021-1 )
  • Recommendation X.402, Message Handling Systems: Overall Architecture, ( see ISO 10021-2 )
  • Recommendation X.403, Message Handling Systems: Conformance Testing
  • Recommendation X.407, Message Handling Systems: Abstract Service Definition Conventions ( see ISO 10021-3 )
  • Recommendation X.408, Message Handling Systems: Encoded Information Type Conversion Rules ( see ISO 10021-1 )
  • Recommendation X.411, Message Handling Systems: Message Transfer System: Abstract Service Definition and Procedures ( see ISO 10021-4 )
  • Recommendation X.413, Message Handling Systems: Message Store: Abstract service definition ( see ISO 10021-5 )
  • Recommendation X.419, Message Handling Systems: Protocol Specifications ( see ISO 10021-6 )
  • Recommendation X.420, Message Handling Systems: Interpersonal Messaging System ( see ISO 10021-7 )
  • MHS Implementor 's Guide, Version 5, Source: ITU (CCITT ) Special Rapporteur Group on Message Handling Systems (Question 18/VII ) and ISO / IEC JTC 1/SC 18/WG 4 SWG on Messaging, ITU, February 22, 1991