Microsoft warns Windows Server patches disrupt Exchange email services

First reported by Cyber Security News at · Updated · 3 sources

Some Exchange Server systems are experiencing webmail sign-in failures and mail delivery problems after October updates. According to Cyber Security News, the affected versions include Exchange Server 2016, 2019 and Subscription Edition; Microsoft has published a workaround and advises administrators not to uninstall the security updates released on October 13, 2026.

Covered by 3 publishers within 9 hours of the first report.

Reporting3

Cyber Security News Microsoft Confirms October Windows Updates Can Break Exchange Server Email Services · Guru Baran
BleepingComputer Microsoft: October Windows Server updates break Exchange sign-in, mail flow · Sergiu Gatlan
Neowin Microsoft issues warning about Exchange Server becoming "unstable" after October 2026 update · Usama Jawad

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Topics Microsoft