Microsoft Releases April 2025 Hotfix Updates for Exchange Server

Microsoft has released the April 2025 Hotfix Updates for Exchange Server 2019 and Exchange Server 2016. The latest updates address issues from earlier versions and enable new functionality for Exchange Server customers.

With this update, Microsoft is strengthening the security of Exchange Hybrid configurations by introducing a dedicated Exchange hybrid application in Microsoft Entra ID. This change helps separate the identities of Exchange Online and Exchange Server. Microsoft says that these updates are a part of the transition from legacy Exchange Web Services (EWS) API to more secure Graph API calls with granular permissions.

“Exchange hybrid customers who require rich coexistence with Exchange Online must act between April 2025 HU release and October 2025. Unless you follow the steps to update to the dedicated Exchange hybrid app (before October 2025) and then update it to Graph permission model (before October 2026), some Exchange hybrid functionality will break,” the Exchange team explained.

How to install the Exchange Server Hotfix updates

Microsoft says that administrators will need to inventory their Exchange Servers and install the latest Cumulative Update (CU). Then, IT admins can use tools such as the Exchange Server Health Checker script and the SetupAssist script to ensure proper installation.

It’s important to note that Microsoft has acknowledged a known issue that causes the Edge Transport service to stop responding when decrypting messages protected by Azure Rights Management (Azure RMS). In Microsoft Exchange Server, the Edge Transport service is a role that handles all mail flow to and from the Internet.

Microsoft notes that the latest Hotfix updates will appear as an optional update for Exchange Server 2019 and 2016. Additionally, this update will be available for customers on the Microsoft Update Catalog in the coming days.

Last week, Microsoft warned IT admins that Exchange Server 2016 and 2019 will reach end of support in October 2025. However, the new Exchange Server Subscription Edition (SE) will be generally available in July. Microsoft is also planning to increase the prices of its standalone on-premises server products (such as SharePoint Server, Exchange Server, Skype for Business Server) by 10 percent on July 1.