We have set up an Exchange 2010 server along side Exchange 2003 for testing and have moved a dozen or so users over, including me. I can send and receive mail OK. I could access my mail before on my Windows phone or Android device before I moved my mailbox by using the IP address on our internet facing router in the settings when I configured my devices.
Inbound connections from the router goes to our Watchguard device which sends mail to the IP of our spam filter, a WatchGuard device. From there it is all sent to the IP address of Exchange 2003 server. Since I moved my mailbox to the Exchange 2010 server I cannot get mail on my phone or tablet anymore. I assume it is because the spam filter is sending everything to the IP of the Exchange 2003 server, but why are the send-receive connectors not putting me thru to the new Exchange 2010 server?