Message Routing in Exchange 2010
Message routing might seem very easy in small organizations like the one in the Contoso scenario, but it gets more complex as the organization grows. For larger organizations, like the Litware scenario described in this book, you definitely have to understand all the possibilities and parameters available to you for planning, configuring, and optimizing message routing.
Message Routing within an Exchange Organization
In Exchange versions prior to 2007 you defined message routing inside an Exchange organization by using routing groups and routing group connectors. Exchange Server 2007 introduced changes to internal message routing that are still valid for Exchange 2010:
The message-routing topology and routing decisions ...