Do you have to be running all W2K3 SP1 domain controllers in your organization before moving to Exchange 2007? No, only the DCs/GCs that will be used by E2K7 have to be W2K3 SP1 (though SP2 works just as well).However, if the setup process finds a W2K DC/GC it will fail. And other processes (once you are in operation) such as Move-Mailbox will also fail. Here is another example:FailedError: Domain Controller 'example.example.org' Operating System version is 5.0 (2195) Service Pack 4. The minimum version required is 5.2 (3790) Service Pack 1.Exchange Manageme   read more »