In preparation for our Office 365 move, I am upgrading our Exchange 2010 to SP3 and then installing the latest roll up. Currently we are on SP2.
I attempted the install for SP3 and it has come up with an error about it not being able to locate a domain controller which is 2003 or later during the readiness check. We recently upgraded our domain controllers to 2019 and demoted the 2008 R2 controllers. We still have one of the 2008 R2 vm's. The domain forest level is 2008 R2. Turns out 2019 isn't compatible with Exchange 2010 as i believe the schema needs to be updated.
Would i be OK joining the 2008 R2 server back to the forest as a controller and then performing the Exchange SP3 upgrade. Then demoting the controller again?