I am in the process of decommissioning my ES2003 server and transitioning to ES2007 on a new server. I am following the instructions from Microsoft knowledge base for removing the last legacy server. When I removed the routing group connector between the old and new server, we stopped receiving all incoming email from the the outside. As soon as I added the RGC back, all mail flowed in. I am not sure how to troubleshoot this situation. I do have both send and receive connectors set up on the ES2007 server. All mailboxes have been migrated to the new server. the firewall is directing all smtp traffic to the new email server.