Our environment consists of several domain controllers, running a mix of Windows Server 2008 Standard SP2 x86 and Windows Server 2008 Standard SP2 x64. The domain functional level is 2008. We also have Exchange in our environment, with roles split amongst several different servers. The Exchange version is 2007 SP1 UR4.
I was about to set up a new domain controller at a new site and was going to install Windows Server 2008 R2 Standard SP1. I have no plans on upgrading the OS of the rest of the domain controllers and raising the domain functional level to 2008 R2 at this time. Before going ahead with the adprep, I decided to do some research.
One comment I saw on one of the Microsoft TechNet forums was that Exchange 2007 doesn't support 2008 R2 DCs until SP1 UR9 or SP2. Unfortunately, I was not able to discern if the poster meant that it won't function correctly in a 2008 R2 functional level domain or if having even one 2008 R2 domain controller in a lower domain functional level will cause issues with Exchange. As such, I am posting here.
Can I run a 2008 R2 domain controller in a 2008 functional level domain without also upgrading Exchange to 2007 SP1 UR9 or higher?