Optimizing the routing of outbound email to the Internet through the nearest SMTP connector is a fairly simple process. Doing so consumes less bandwidth on internal WAN links, and email reaches the Internet quickly while traversing less of the internal network. To achieve such a configuration, group servers together into geographical routing groups, each of which contains a dedicated SMTP connector. These dedicated local SMTP connectors have a low cost associated with them, compared with the aggregate costs for SMTP connectors in other routing groups. Because Exchange Server will route email to the Internet through the lowest-cost connector available, Internet-bound email will generally use the local SMTP connector. Figure A shows a sample configuration in which email sent to the Internet from an Exchange mailbox server in a given routing group will always use the SMTP connector in the same routing group because the cost (10) is always lower than the cost to use any other SMTP connector (minimum 110, maximum 210).
