Exchange 2010 SP3 RU29 with 2019 Domain Controllers

[muhoboika]

Hello, I wonder if someone can give a bit of clarification regarding the Microsoft's matrix for Exchange 2010 support here.

docs.microsoft.com/en-us/exchange/plan-and-deploy/supportability-matrix?view=exchserver-2019

I am currently upgrading domain controllers from 2008 R2 (2 of them) to 2019, and have already promoted and setup 2 new ones. Domain and Forest level is still set to 2008 R2. All FSMO roles have been transferred and Exchange 2010 successfully picked up and using see the new 2 2019 DCs.

Now Microsoft's site says it does not support 2019 environment? This is the part that concerns me, because it clearly does.

I haven't demoted 2 old DCs yet, but based on all info I could find Exchange is already using 2019 DCs.

Also all flags look proper in Exchange Discovery event viewer (event 2080)

Process STORE.EXE (PID=5108). Exchange Active Directory Provider has discovered the following servers with the following characteristics:
(Server name | Roles | Enabled | Reachability | Synchronized | GC capable | PDC | SACL right | Critical Data | Netlogon | OS Version)
In-site:

CDG 1 7 7 1 0 1 1 7 1 for both new 2019 DCs.

Should I be concerned with demoting 2 old ones? Based on the matrix Exchange 2010 should work with 2016 functional level, so if I were to raise it to that level after demoting the old ones everything should still be OK? 

Is there another test I can run to make sure exchange will still be fine after demoting  old ones?

I was thinking explicitly excluding 2 old ones using -StaticExcludedDomainControllers on the exchange to make sure its not using them at all? Will that be sufficient to make sure?

I have attached a screenshot from exchange console with more info.

It would be nice to find why Microsoft is saying that Exchange 2010 is not able to communicate with 2019 DCs...

Thanks

[#2]

The document does not outline what appears to work or not work but instead documents what has been tested and is currently supported. If it's working for you then that's a good sign but if some problems arise it simply is not a supportable configuration. The risks / burden of support is left to end user.

[#3]

@Dave Patrick Thanks

So If I were to promote another DC but 2016 and point Exchange to use it, then it becomes supportable configuration correct? 

[#4]

@Dave Patrick  Also the document seems to clearly state:

The following table identifies the Active Directory environments that Exchange can communicate with. 

This is the confusing part

[#5]

My read of the document is that if 2019 domain controllers are introduced then it would be an untested unsupported configuration.