How do messages get from an Exchange 2000 server to an Exchange 5.5 server in the same site/routing group?
An Exchange 2000 server evaluates whether the server is in the same routing group or not. If it is, then the server sends the message through the Message Transfer Agent (MTA), which creates a direct local area network (LAN), MTA, RPC connection. If it is not, the server routes the message to the routing group of the destination server through connectors.