Today, we are announcing the availability of the 2025 H1 Cumulative Update (CU) for Exchange Server 2019 (aka CU15). This is the last CU we will release for Exchange Server 2019.
CU15 includes new ...
Updated Feb 26, 2025
Version 9.0
Blog Post
Can you provide clarity around AD Forest & Domain functional level requirements when installing CU14 or CU15 on Windows Server 2025?
Do we just need one DC running Windows Server 2025 or to all DCs need to be 2025 with the forest and domain functional level upgraded to 2025?
The statement for 2025 support is unclear.
EDIT: After reading https://learn.microsoft.com/en-us/Exchange/plan-and-deploy/supportability-matrix?view=exchserver-2019#supported-active-directory-environments I believe that functional level 2025 is now supported but not mandated.
Support for Windows Server 2025
We are happy to announce that both CU14 and CU15 include support for running Exchange Server 2019 on Windows Server 2025 and in organizations that use Active Directory servers that run Windows Server 2025.
- LukasSMSFT
Microsoft
Windows Server 2025 functional levels are not supported. Running Domain Controller with Windows Server 2025 OS as well as installing Exchange Server 2019 CU14/15 on Windows Server 2025 is supported.
Do all our domain controllers need to be running Windows Server 2025, or just one?
- Nino_Bilic
Running Windows Server 2025 domain controllers is an option, not a requirement. All that we are saying is that we support Windows 2025 DCs now, not that we require them.
thanks for clarifying the 2025 Domain Controller support
is the Windows Server 2025 functional level expected to be supported by the Exchange SE release?- Nino_Bilic
When and if that comes (I expect it to come at some point but nothing to announce) - it would not come before SE CU1 at the very least (SE RTM is effectively locked to E2019 CU15 features and everything it supports). But again - nothing to announce as of now.
