Routing

MSMQ establishes a direct connection (a session) using the underlying protocol, if possible. When a direct connection is not possible or not allowed, MSMQ uses its own routing system. MSMQ routing occurs when one or more of the following conditions exist:

When a session cannot be established between the sender and the receiver (for example, the source and target computers do not share a common CN or the target computer is offline).
When InRSs or OutRSs are defined for the sender or receiver.
When messages must travel between two sites, and one or both sites have a site gate defined.

MSMQ servers make two assumptions about your MSMQ network: Intra-site routing is fast and inexpensive, while inter-site routing is slow and expensive.