Microsoft Exchange Server can accommodate mail messages sent to recipients that are on the local server, on other Microsoft Exchange Server computers, and on foreign systems. Communication between a local server and servers that are in other Microsoft Exchange Server sites or foreign systems is accomplished by routing messages through gateways, which are called connectors. Each connector has at least one path, called an address space, associated with it. Each address space describes an address format required by the type of system for which it is responsible. The connector's address spaces are used by the message transfer agent (MTA) to select the connectors that are candidates for routing a particular message.
To connect a local server to another Microsoft Exchange Server computer in a remote site, Microsoft Exchange Server uses one of the following:
To connect a local server to a server in a foreign system, Microsoft Exchange Server uses one of the following: