I changed our NAT policy to point to our new Exchange 2010 server this morning, with legacy.mycompany.com created as a legacy domain name. Everything seemed to be flowing just fine (internal email, OWA, etc...), except all my 2003 users lost connection from their mobile devices (iPhones). What am I missing for ActiveSync to work? Again, all users are still on the Exchange 2003 server. I was getting ready for the 2010 to "go live", and as soon as I switched the MX record, everything was fine except the ActiveSync clients.
What did I forget to do?