Summary
Microsoft released a Hotfix Update (HU6) for Exchange Server Subscription Edition (SE). The release contains no security fixes but delivers a long-awaited functional change that hybrid administrators have been preparing for since 2025: it allows organizations to start switching their Exchange Server hybrid rich coexistence from Exchange Web Services (EWS) to REST-based Microsoft Graph API calls.
HU is available for the following specific version of Exchange Server:
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What Was Released
Hotfix Update 6 (HU6) for Exchange Server Subscription Edition (SE) RTM was released on May 7, 2026, identified as KB5081755. This update addresses non-security issues and may introduce new features, with all included fixes slated to be rolled into a future Cumulative Update for Exchange Server SE.
Microsoft Graph Support for Hybrid
The addition in this hotfix is Microsoft Graph support for hybrid features in Exchange Server SE. This aligns with broader Microsoft messaging around transitioning Exchange Server hybrid rich coexistence away from the legacy Exchange Web Services (EWS) protocol and toward the Microsoft Graph API. For organizations running hybrid Exchange environments, where on-premises Exchange coexists with Exchange Online, this marks a meaningful step toward a more modern, supportable integration architecture.
Update Replacement
HU6 supersedes the previously released February 10, 2026 security update (KB5074992) for Exchange Server SE RTM. Administrators who have not yet applied the February update can apply HU6 directly.
How to Install
The update can be obtained in two ways:
- Windows Update — the update will appear automatically through the standard Windows Update process.
- Microsoft Download Center — a standalone installer (ExchangeSE-KB5081755-x64-en.exe) is available for manual deployment.
Recommendation
Organizations running Exchange Server SE in a hybrid configuration should prioritize this update, as it begins enabling the transition to Graph API-based hybrid features.
As always, test in a non-production environment before deploying to live infrastructure. For full build number and compatibility details, consult the Exchange Server Updates release notes for full build number and compatibility details.
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