database connection

On October 13, 2026, Microsoft released security updates for Windows Server that unintentionally affected Microsoft Exchange Server, causing significant disruptions approximately 24 hours after installation. Users reported issues such as database services failing, resulting in unresponsive email and Outlook Web Access access. Microsoft acknowledged the problem and is investigating it. The updates targeted supported Windows Server and Microsoft Exchange versions 2016, 2019, and SE. By October 15, reports of severe issues, including the inability to connect to the server and halted email delivery, emerged. The error message associated with the disruption is "MapiExceptionMdbOffline: Unable to make connection to the server. (hr=0x80004005, ec=1142)." Despite these issues, the Exchange Admin Center still showed databases as connected and mounted. Unofficial workarounds, including a registry edit and a PowerShell script, have been suggested to mitigate the problems.