The Exchange product group released the May 2025 Hotfix Updates for Exchange Server 2019 and Exchange Server 2016.

Hotfix updates do not contain security fixes, but address issues. They also might introduce or add support for functionality changes, such as dedicated Exchange hybrid app support added in the April hotfixes.

Exchange	Download	Build	KB	Supersedes
Exchange 2019 CU15	Download	15.2.1748.26	KB5057651	KB5050672
Exchange 2019 CU14	Download	15.2.1544.27	KB5057652	KB5050673
Exchange 2016 CU23	Download	15.1.2507.57	KB5057653	KB5050674

Changes

Issues addressed in these hotfixes are:

• Journal message returns “ConversionFailedException”
• Calendar print doesn’t work in OWA from Exchange 2019 CU14 onwards
• Edge Transport service stops responding after installing November 2024 SU or Exchange 2019 CU15​​​​​​​
• StoreWorker fails because of BaseViewOperatorDefinition​​​​​​​

Dedicated Exchange Hybrid Application

A gentle reminder that since the April 2025 security updates, Exchange hybrid supports the dedicated Exchange hybrid app. The dedicated Exchange hybrid app becomes mandatory in October 2025 for continued cross-premises functionality (free/busy, a.o.). To make the required changes related to the Graph permissions model you have some more time, as that will become required in October 2026. For more information, please visit this link.