Information that indicates which address types and subtypes can be handled by connectors and gateways for Microsoft Exchange Server.
This information is used to determine how messages are routed. Each time a new connector or gateway is installed, a new address space must be created for that connector or gateway. For example, if a message were being routed through the Internet Mail Service to the address firstname.lastname@example.org, the address type would be SMTP and the address space would be microsoft.com. Other address types include MS Mail and X.400.
Each address space can be assigned a cost value, which is used for optimizing outbound message routing. The lower the cost value of an address space, the less it will be used by the connector. If two address spaces have the same cost value, each route will be given roughly equal priority in the routing process.