PENDING Windows Server 2025 with Exchange Server 2019 CU14

[Ase]

Hi All,
Have anyone of you upgraded the host OS of a Exchange Server 2019 CU14 to Windows Server 2025?
I know it is not supported, but have anyone of you tried?
This is the server lagging behind and dont mind if its not officially supported, just want to know if I break Exchange or not.

Thanks,
Ase

 

[EvanMael]

Honestly? I wouldn't touch that with a ten-foot pole.

In-place OS upgrades on Exchange are a recipe for disaster. Microsoft doesn't support it for any OS version, not just 2025. Exchange is so tightly coupled with IIS, AD, .NET and a bunch of Windows components that an upgrade will almost certainly break something. Maybe not immediately, but you'll start seeing weird stuff: mail flow issues, OWA dying, databases refusing to mount...

I get it, the server is lagging behind and you just want to move forward. But trust me, the "quick" path here will cost you way more time in troubleshooting.

The clean way: spin up a fresh Exchange 2019 on Server 2022 (that's the latest supported combo), migrate your mailboxes, then retire the old box. It's more work upfront but you'll sleep better at night.

If you really want Server 2025, wait for Exchange SE. Microsoft said it's coming H1 2025 and it should officially support it.

Good luck!