We are in the process of migrating from Exchange 2007 to Exchange 2010. I'm working through the process of implementing the movement to using the CAS 2010 environment with the same namespace (mail.company.com) and then have looked at using the legacy.company.com namespace for the 2007 environment.
In trying to test the Activesync clients it is painful to understand if things will work in a reasonable fashion. My thinking is we can simply remove the EXTERNAL URL for ACTIVESYNC and allow the 2010 environment to proxy the user information from the 2010 CAS environment. This will allow user to NOT have to change any activesync device setting and it will be a seamless transition.
So in Summary:
Activesync: Change ExternalURL to null on the 2007 servers to force 2010 CAS to proxy the information.
Outlook Anywhere - disabled on the 2007 CAS Server so 2010 CAS will proxy the information.
OWA - See no reason to do the same Change the ExternalURL to null so 2010 CAS will proxy the information.
Does anyone see any issues/problems with this approach?
THANKS