Routing

A mail message can be a P1 message, a probe, or a report. Messages to each recipient are routed individually. If the recipient is local to the originating MTA, local routing takes place. If it is not local, remote routing takes place.

Messages are submitted to the Microsoft Exchange Server computer by a local user, by another Microsoft Exchange Server computer, or by a foreign mail system through a connector or gateway.

Messages can be routed to the following:

• A recipient on the same server computer
• A recipient on a different server computer in the same site
• A recipient in a different site or foreign system

Routing in the Microsoft Exchange Server mail system is carried out by the MTA. The MTA can send mail externally to:

• Microsoft Exchange Server MTAs in the same site using remote procedure calls (RPCs)
• Microsoft Exchange Server MTAs in a different site through the Site Connector or Internet Mail Service
• Microsoft Exchange Server MTAs in a different site through a Dynamic RAS Connector
• Remote X.400 MTAs through an X.400 Connector, which can be configured for various transport protocols such as X.25, Transport Control Protocol/Internet Protocol (TCP/IP), or Transport Class 4 (TP4)
• Gateways (for example, Microsoft Mail Connector)