We recently installed an Exchange 2010 server to coexist with our Exchange 2003 environment which is just a single server in a single domain and organization. When Exchange 2010 was installed, it automatically created the routing group connector (RGC) between the two systems and it appeared at first all was well. We realized later on that Internet-bound email from Exchange 2003 takes 2-5 hours to send out. (There are some that only take a few minutes and I'm not sure why these go out faster than the others). The RGC queue constantly has 120-150 items in it. We also use a smart host that the Exchange 2010 Internet Email Send Connector points to. I verified that the RGC on the 2003 side no longer points to the smart host. All of our mailboxes are still on the 2003 side as we have not yet begun our migration of mailboxes. Normally I would say that something is configured incorrectly but the mail usually goes out. (Though we are seeing some email that expires before getting out and the user eventually gets an NDR). What could be causing this? I've looked all over the net for ideas and I'm just not seeing anything that matches our situation.