Are Your Exchange Servers Vulnerable to These Critical May 2025 Hotfix Issues?

Why Haven't You Applied These Game-Changing Exchange Server Updates Yet?

Microsoft released May 2025 hotfix updates for Exchange Server 2016 and 2019 on May 29, 2025. These updates focus on fixing non-security issues rather than addressing security vulnerabilities. I want to help you understand what these updates contain and why they matter for your Exchange environment.

What These Updates Include

The May 2025 hotfix updates target specific Exchange Server versions without introducing new security patches. Instead, they address operational problems that have been affecting administrators. The updates are available for Exchange Server 2019 CU14, Exchange Server 2019 CU15, and Exchange Server 2016 CU23.

These hotfixes contain cumulative improvements, meaning they include previous fixes plus new solutions. The updates also maintain support for the dedicated Exchange hybrid application that was introduced in April 2025.

Critical Issues Fixed

The May 2025 updates resolve several important problems that have been troubling Exchange administrators:

Edge Transport Service Problems

The most significant fix addresses the Edge Transport service stopping after installing the November 2024 security update. This issue had been listed as a "known problem" in recent releases. If you previously worked around this issue, you'll need to manually remove your workaround according to the KB article instructions.

Calendar Printing Issues

The updates fix calendar printing problems in Outlook Web Access that started occurring from Exchange 2019 CU14 onwards.

Journal Message Errors

Administrators experiencing "ConversionFailedException" errors with journal messages will find relief with these fixes.

StoreWorker Failures

The updates address StoreWorker failures related to BaseViewOperatorDefinition issues.

Installation Challenges and Solutions

Some administrators have encountered installation difficulties with these updates. Common problems include processes appearing to be in use during installation, which can cause the installer to fail.

If you experience installation issues, try these approaches:

• Disable antivirus software completely before starting the installation
• Run the installer from an elevated command prompt
• Use the retry option if the installer reports processes in use
• Ensure the World Wide Web Publishing Service and IIS Admin Service are properly configured

One administrator reported that canceling a failed installation left all Exchange services in a disabled state. If this happens to you, manually set the services back to automatic startup and reboot the server. Pay special attention to the World Wide Web Publishing Service, as the installer may change its startup type.

Update Installation Process

Microsoft recommends following a structured approach for installing these updates:

First, inventory your Exchange servers using the Exchange Server Health Checker script to determine which updates you need. This script identifies servers that are behind on cumulative updates, security updates, or manual actions.

Next, install the latest cumulative update using the Exchange Update Wizard, which provides step-by-step directions for moving from your current version to the target version.

After installation, run the Health Checker again to verify that no additional actions are required. If you encounter errors during or after installation, use the SetupAssist script for troubleshooting.

Hybrid Application Requirements

These updates include continued support for the dedicated Exchange hybrid application. This becomes mandatory in October 2025 for cross-premises functionality like free/busy information. You have until October 2026 to make the required changes related to the Graph permissions model.

Why These Updates Matter

Even though these are non-security updates, they address real operational problems that can disrupt your Exchange environment. The Edge Transport service issue alone has caused significant problems for many organizations. Calendar printing failures affect user productivity, and journal message errors can impact compliance requirements.

The cumulative nature of these updates means you get all previous fixes plus the new ones. This approach reduces the complexity of managing multiple individual patches.

Installing these May 2025 hotfix updates will improve your Exchange environment's stability and resolve several nagging issues that have been affecting administrators. While they don't contain security fixes, they address operational problems that can significantly impact your users' experience and your system's reliability.