Hello,
We currently have Exchange 2013 CU21 on-prem servers in our primary and secondary Data Centers with Hybrid configured with Office 365. Majority of mailboxes have been migrated to O365, with just a few remaining on-prem. In primary and secondary Data Centers, Domain Controllers are on server 2016. We have a few remote sites aswell in which the Domain Controllers are on server 2019, and because of that, our AD schema version displays as 88 which I guess got updated when 2019 DCs were installed. At the moment, the domain and forest functional level is 2012
I am now planning on upgrading on-prem exchange to exchange 2019. both Exchange 2013 and Exchange 2019 will co-exist temporarily. to introduce Exchange 2019 into the environment, I will have to raise the domain and forest functional levels to Windows server 2016 (probably can raise to 2012 R2 aswell, but might as well go to latest).
Looking at the pre-requests for Exchange 2019, and Exchange 2013 co-existence, it mentions that Exchange 2013 supports 'Windows Server 2016 Active Directory servers ' Operating system environment. So i assume even if the AD Schema version is set to 88 (which is for Windows Server 2019 OS), i can still get by because in the sites where Exchange 2013 is installed, and Ex2019 will be installed, all DCs are on server 2016 OS? Can i also safely raise the domain and forest functional levels to windows server 2016 without impacting Ex2013?
