The latest Cummulative Update for Exchange Server 2019 has been postponed again Originally, CU 15 for Exchange 2019 was supposed to be released in December 2024, but the release has been postponed to January 2025. On last day in January the message appeared on the Exchange Team Blog that CU 15 had been postponed again.
The CU15 will be the last CU for Exchange 2019 and brings the Exchange Server to the same code base as Exchange Server SE Edition. Exchange Server SE will not contain any new features at release, but will only adjust the branding and EULA to Exchange Server SE. Therefore, for the first time, an in-place update from Exchange Server 2019 CU15 to Exchange Server SE is supported. Only the license changes here. So as soon as CU15 for Exchange 2019 has been published and installed, the "migration" to Exchange Server SE is basically completed with a small update.
An in-place upgrade of the operating system is not supported. If Exchange Server 2019 is currently running on Server 2019 or Server 2022, a classic migration is required (installation of Exchange Server on the new operating system and moving the mailboxes).
There is one more important piece of information: Exchange Server 2019 CU14 (i.e. the current version) has been released for Windows Server 2025. This means that you can start migrating from Exchange Server 2019 now. In concrete terms, this means that Exchange Server 2019 CU14 can be installed on Windows Server 2025. With the installation of Exchange Server 2019 CU15, you will already have the Exchange Server SE code base on Windows Server 2025. As soon as Exchange Server SE is released, you will only need to install the in-place upgrade and you will be up to date: Exchange Server SE on Windows Server 2025.
However, all of this must be completed by October 2025, as this is when support for Exchange Server 2019 and Exchange Server 2016 ends. Microsoft is currently ruling out an extension of support.
The reason for the further postponement of CU15 are problems with the update, which were found in the Insider Program (TAP). CU15 is supposed to contain new features, so you should be a little careful when releasing and installing it...
