Gateway Overview

In Microsoft Exchange Server, a gateway is an interface connecting two or more electronic messaging systems that, typically, have different message and address formats. In general, the function of a gateway consists of several actions:

• Receipt of a mail message. When a user sends a message, Microsoft Exchange Server determines whether the message can be delivered to that recipient by Microsoft Exchange Server or must be transferred by a gateway. If a recipient is on a foreign mail system, the message is assigned to the appropriate gateway. The gateway then receives the message from its MAPI folder MTS-OUT.
• Message translation. The translation of messages between different mail systems is accomplished within Microsoft Exchange Server by a conversion engine. One message characteristic is the message class, a description providing information about the set of properties defined for the message. Upon receipt of a message, the gateway examines the message class and determines the appropriate conversion engine to invoke.
• Delivery of the translated message. After translation of the message, the gateway examines the contents of the Message Transfer Envelope to determine the delivery information for the message. The message is then delivered based on the contents of the recipient list.