Microsoft releases several Hotfix Updates (HUs) for Microsoft Exchange Server on September 8, 2025. It includes fixes for non-security issues and introduces new features. These fixes and features will also be included in later Cumulative Updates for Exchange Server SE.
Exchange Server Hotfix Updates
The September 2025 HU is available for the following builds of Exchange Server:
Read more on how to Install Exchange Hotfix/Security Update.
If you are not on these Exchange Server CU versions, please update right now and apply the above patch.
Read more on how to Install Exchange Cumulative Update.
Issues fixed in this update
FAQs
We installed the last Security Update. Should we install the later Hotfix Update?
Exchange Server HUs are optional updates, but they might introduce features or fixes that your organization can benefit from.
We did not yet install the earlier Security Update. Do we have to install the last available SU first before installing the later HU?
All of Exchange updates (HUs or SUs) are cumulative. Therefore, a newer HU will contain all the changes that a previous, older SU has. If you have not installed the older SU yet, you can install the newer HU directly and skip the older SU.
Our Exchange servers update automatically through Windows / Microsoft Update. Will our servers automatically install the HU update?
HUs will appear as an optional update for your servers. The update will also be available on the Microsoft Update Catalog after a few days of delay.
Will the new features and fixes released in the HU also be rolled into future updates, or must we install this specific HU to get them?
Content of this HU will be included in subsequent updates for Exchange Server.
Can HUs be uninstalled (if the need arises)?
Yes. HUs, like SUs, can be uninstalled.