[German]The security updates for Windows Server released by Microsoft on October 13, 2026, are also affecting Microsoft Exchange Server. Reports on my German blog and across the internet indicate that database services stop working approximately 24 hours after the updates are installed, and email and OWA access become unresponsive. Microsoft has acknowledged the issue and is investigating it. A German blog reader made an analysis that sheds light on the underlying causes. In addition to periodic server reboots, there appears to be an unofficial workaround involving a registry edit to prevent the database error. A PowerShell script might help also.
A Look Back at the Updates and Exchange Issues
Microsoft released on October 13, 2026 security updates (SU) for Windows Server versions still under support, as well as for the supported Microsoft Exchange versions 2016, 2019, and SE (see links at the end of the article).
On October 15, 2026, there was a flood of reports describing massive problems with Microsoft Exchange. One affected user sums it up in this comment:
Mail Transfer stucked in Que after 24 Hours installing the KB. This Problem is on 3 Exhcange Servers SE
The Microsoft Exchange Mailbox Replication service was unable to process jobs in a mailbox database.
Error: MapiExceptionMdbOffline: Unable to make connection to the server. (hr=0x80004005, ec=1142)
Restart Solve this Problem.
Serious issues lems occur because the database connection is lost. On affected Exchange servers, the following error message appears:
MapiExceptionMdbOffline: Unable to make connection to the server. (hr=0x80004005, ec=1142)
The result: Users can no longer connect to Exchange, and emails are no longer being delivered. However, in the Exchange Admin Center, the databases continue to be displayed as connected and mounted. It affects on-premises Exchange servers as well as Exchange Online.
On October 15, 2026, Microsoft updated the Tech Community post with the following announcement and confirmed the issues.
Inofficial analysis and workarounds
Within the comments in the Tech Community post users mentioned a registry entry that shall avoid Exchange hangs. But still no explanation, how and why it helps. A German blog reader made an analysis that sheds light on the underlying causes. And there are inoffcial workarounds, avoiding a Windows Server restart. Details may be found within my German blog post Microsoft analysiert Windows/Exchange Server-Probleme durch Oktober 2026-Updates – Workouts verfügbar. Use the build-in translator, provided by my German blog, to read the article in English or other languages:
