I'm deploying a Windows 2012 R2 server for one of our customers. We do have a few stragglers running Windows XP SP3.
I have seen that XP machines can be joined to a Windows 2012 server domain. My question is however, do I need to keep the Forest Functional Level at anything below Windows Server 2012R2? (The other options are Windows Server 2008 / Windows Server 2008R2 / Windows Server 2012).
Also note - I will be installing Exchange 2013 on a different machine on the same domain so I cannot drop the functional level beyond what Exchange 2013 will require.
Thank you in advance.