Understanding and Configuring Message Routing and Transport

Together, message routing and transport are responsible for message delivery internally and externally. Message routing is the way that messages flow between servers in the organization and to other servers outside the organization. Your routing topology, based on the routing groups and connectors you define, dictates the path these messages take to reach their final destination. Transport determines the way that messages are delivered.

Simple Mail Transfer Protocol (SMTP) is the transport protocol that Exchange servers use to communicate with each other and send messages using the routing topology. SMTP is part of the Microsoft® Windows Server™ 2003 or Microsoft Windows® 2000 Server operating system. When you install Microsoft Exchange on a server running Windows Server 2003 or Windows 2000 Server, Exchange extends SMTP to support additional SMTP commands for additional functionality. This functionality includes the ability to communicate the link state status, available messaging routes status, and other Exchange functionality.