Exchange 2010 SP3 and DFL 2016

I have a customer with a domain with an Exchange2010 Sp3 . There are 3 2016 domain controllers and the domain functional level has been raised to 2016.
Now they want to create a hybrid exchange environment. But when i run the Pre Deployment Analyzer i get an error no Domain Controller found. I understand that 2016 DFL is not supported but how can i solve this problem form here?
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Justin EvansCommented:
unfortunately,  the domain functional level is a one way move,  if you have moved to windows 2016 DFL there is no way back unless you do a domain restore to before the functional level was moved.  which leaves you with one other option to upgrade there exchange 2010 SP3 environment to Exchange 2016.
Todd NelsonSystems EngineerCommented:
Always check the Exchange Supportability Matrix  before upgrading any environment with Exchange in it ...

With that said, Exchange 2010 is not supported in any environment with Windows 2016 DCs regardless of domain or forest functional level.  

Therefore, you will in someway need to introduce Windows 2008 R2 (at a minimum).  Take a look at this link for the potential to lower the DFL/FFL to get some Windows 2008 R2 or 2012 R2 DCs installed ...  You will most likely need to remove/demote the Windows 2016 DCs to complete the transition to Exchange 2016.  After the transition is complete (removing all Exchange 2010 servers), then you can introduce the Windows 2016 DCs; but not before then.  If you do it before, you won't be able to remove the Exchange 2010 servers.
GnukkelAuthor Commented:
Thanks for your suggestions would it not be possible to setup a connection with Office 365 and move the mailboxes?
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Todd NelsonSystems EngineerCommented:
would it not be possible to setup a connection with Office 365 and move the mailboxes?

You should be able too.  Nevertheless, you wont' be able to remove Exchange 2010 properly or add Exchange 2016 for hybrid management.
GnukkelAuthor Commented:
I downgraded FFL and DFL with this document.

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GnukkelAuthor Commented:
I called microsoft and they pointed me to this document.
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