Three objects appear in the Microsoft Exchange Server directory to represent the gateway. The first is a Mail-Gateway object that represents the gateway service. The second is an Admin-Extension object that represents the administrator extension DLL. The third is an Addr-Type object that represents the family of addresses handled by the gateway, and the proxy generation DLL that converts between Microsoft Exchange Server addresses and foreign addresses.
The Mail-Gateway object represents the gateway service itself, whether it is running on the same computer as the server or on a separate computer.
To address mail to foreign systems, Microsoft Exchange Server uses an Addr-Type directory object that registers the existence of the foreign address type, and points to the location of the proxy generation DLL.
The Addr-Type object is associated with the Mail-Gateway object in the gateway address routing table (GWART). The GWART contains information about the gateways available to Microsoft Exchange Server and the address types associated with each one. When a message needs to be routed through a gateway, the GWART is used to determine the appropriate gateway to use based on the address type of the recipient. The Addr-Type object also points to the location of the proxy generation DLL.
Other directory objects are used to describe address entry templates to assist users in entering new addresses, and to describe templates for entering per-message and per-recipient message options, although these do not directly represent any components of the gateway.
For more information, see Objects, Addr-Type Object.