I just migrated about 500 users to my new Exchange 2007 servers. I still have about 100 users on the Exchange 2003 server. Whenever any of the Exchange 2007 users try to schedule a new appointment and they click on SchedulingAssistant, they get a message that
No free/busy information could be retrieved.
It doesn't matter if I add attendees that are on the old server or the new
server. Email messages flow just fine. The Exchange 2007 users use Outlook
I have 1 Hub Transport/CAS server running with Exchange 2007 with SP3 and Mailbox servers running with Exchange 2007 SP1 in CCR.