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I am trying to install Exchange Server 2019 on a physical server running Windows Server 2016 in a fresh environment. No other Exchange running. I have already installed all prerequisites for Server 2019. I ran the powershell commands to /PrepareSchema, /PrepareAD, and /PrepareAllDomains. Everything went exactly as expected.
I then rebooted and ran the setup.exe file for Exchange Server 2019. The install kicked off but failed immediately because of an unsupported operating system. Obviously, I checked the box to install both the Mailbox Role and the Management Tools.
When I ran the /PrepareAD command, I got the message that no Exchange 2016 roles were found and after this, none would be allowed. I thought I was fine because I was installing 2019 roles, right? Clearly I was wrong.
So now that I've prepared AD for an Exchange 2019 install, how can I now install Exchange 2016 on this server? I am allowed to install Exchange 2016, but for security reasons, I can not upgrade the server OS to Server 2019.
I have gone back through the instructions and prerequisites and I can't believe I missed this little fact. "Mailbox role must be on Server 2019." But it's too late to go back now.
I appreciate any help.
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Hi @Mark Zaetz
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Hi @Mark Zaetz
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Ok, because you ran /PrepareAD, you cant go back, sorry.
You wont be able to install Exch 2016 at this point since it was not already installed before the 2019 PrepareAD was run :(
Your only supported option is to install Exchange 2019 on a 2019 server.
That wouldnt work unless you did a full forest restore. I would recommend against that. The AD forest schema has been updated as well when 2019 prep steps were ran.
I did take a backup of AD prior to the change. Any chance I can use that to rebuild it?
Honestly, I wouldnt do that in a production environment. If this was a test forest and you can afford to lose it, then you may want to try that.
It is a production environment but it is really small. Only one domain with two DCs and two member servers. Only about 30 users and clients.
Do I have any options on getting Exchange 2016 in this environment? Like standing up a second domain with a trust relationship? Any other possible options? I can't migrate to Server 2019 until the end of 2023 and I need an email solution asap.
I really appreciate any ideas.
Well, thats the dilemma.
Doing anything to force this to work would be unsupported.
( Like changing the schema and object values to 2016 values)
You could do a full forest restore or restore your AD backup and start over, but you risk something going seriously sideways and making things worse
https://learn.microsoft.com/en-us/windows-server/identity/ad-ds/manage/ad-forest-recovery-guide