The primary task of a gateway is to transfer messages between a Microsoft® Exchange system and a foreign messaging system. Though much of the architecture of message transfer has changed in Exchange 2000 Server, this primary task and the means of performing it remain essentially the same. This is because gateways still interact with the same transfer mechanism, the message transfer agent (MTA), as they did in earlier versions of Exchange. Although the role of the MTA has been reduced in the overall structure of Exchange 2000 Server, the MTA still operates to support EDK gateways and foreign connectors that use the X.400 transport protocol.
The following is a brief description of the message transfer process:
The Exchange server delivers outgoing messages to the gateway by attaching them to a special message created by the MTA, called a message transfer envelope (MTE). The server then delivers the MTE with the messages to the MTS-OUT folder of the gateway. The gateway takes the messages from the MTS-OUT folder and delivers them to the foreign system. For incoming messages, the gateway uses the information in the incoming message to create a MAPI message, which it then puts in its MTS-IN folder.
The MTE provides a list of recipients to whom the gateway must deliver the message. The message is treated as an attached message object within the MTE. Your gateway must be able to process MTE information and deliver the attached messages. It also must be able to transfer several types of reports that inform message originators and recipients about message status.
The following topics provide more information about message transfer: