Active Directory - Lowering the FFL/DFL

Hi all,

I have two On-Prem Exchange environments; the legacy Exchange 2007 SP3 RU 16 (empty databases, no PF), and our Production Exchange 2013 CU22 infrastructure, which holds 1,400 mailboxes.  We need to retire the legacy, empty Exchange 2007 SP3 RU16 only.  We are keeping the Hybrid infrastructure for the foreseeable future, as we're moving to Exch Online in 4Q.<o:p></o:p>

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Since we need to retire only the legacy Exchange 2007 SP3 RU 16 infrastructure, and our current AD structure is a mix of Windows 2012 R2 and Windows 2019 Datacenter with aFFL/DFL Windows 2012 R2, will it be possible to uninstall the legacy Exchange 2007 SP3 RU 16 infrastructure if we lower the FFL/DFL to Windows 2008R2?  <o:p></o:p>

Also if anybody has a list of any known issues or caveats to lowering the FFL/DFL from Win2012R2 to Win2008R2, that would be helpful?<o:p></o:p>