Microsoft Extends Testing for Final Exchange Server 2019 Update – What it Means for Businesses

Microsoft has yet to release the final cumulative update (CU15) for Exchange Server 2019 due to technical issues. The company has outlined some of the reasons for the delay, but it has not provided a new expected release date for the update.

In December, Microsoft announced plans to push the final cumulative update for Exchange Server 2019 into 2025. The company acknowledged feedback from customers who indicated that December was not an ideal time for Cumulative Updates. The company noted that CU15 (also known as the H1 2025 CU) was initially expected to arrive in early January 2025. However, Microsoft has confirmed a further delay due to the complexity of new features and customer-reported issues from Microsoft’s Technology Adoption Program (TAP).

Development of a new Exchange Server 2019 CU15 build

To address these issues, Microsoft is developing a new version of CU15, which requires additional testing to ensure quality and reliability. However, this extended testing has further delayed the release to the general public.

“We have committed to Exchange Server CU15 being the ‘code equivalent’ to Exchange Subscription Edition (SE) RTM release (other than updates released in interim, as well as changed branding and EULA). Therefore, CU15 is the last chance that we have if we want to release any Exchange features before Exchange SE CU1. CU15 does include new features, which added complexity to this release,” the Exchange team explained.

End of support coming soon for Exchange Server 2019

Microsoft will end support for Exchange Server 2019 on October 14, 2025, while Exchange Server Subscription Edition (SE) is expected to launch later this year. The CU15 update will allow users to upgrade their existing Exchange Server 2019 installations to a version nearly identical to the initial release of Exchange Server SE.

It’s good to see that CU15 is undergoing more thorough testing compared to the problematic November 2025 Security Update, which caused issues with transport rules and email services. However, organizations must act quickly to update their systems before the end-of-support deadline for Exchange Server 2019 in October.

Microsoft advises users still running older Exchange Server versions to first upgrade to Exchange Server 2019 and then install the latest update. Once Exchange Server SE becomes available, users can perform an in-place upgrade from Exchange Server 2019 to Exchange SE.