# Microsoft fixes Exchange sign-ins broken by Windows Server updates

Source: [BleepingComputer](https://www.bleepingcomputer.com/news/microsoft/microsoft-fixes-exchange-sign-ins-broken-by-october-windows-server-updates/) · 2026-11-11 · Security
Page: https://themorning.dev/story/microsoft-fixes-exchange-sign-ins-broken-by-windows-server-updates-6cc65111539402d1
Kind: outage · Impact: medium

## In brief

- Microsoft has fixed Outlook sign-in issues on Exchange Server systems.
- The same fix addresses mail delivery problems on those systems.
- The issues appeared after installing the October 2026 Windows Server security updates.

## Why it matters

Administrators who installed the October 2026 Windows Server updates on Exchange Server may have seen broken Outlook sign-ins and mail delivery until this fix was applied.

## Coverage

- [Microsoft fixes Exchange sign-ins broken by Windows Server updates](https://www.bleepingcomputer.com/news/microsoft/microsoft-fixes-exchange-sign-ins-broken-by-october-windows-server-updates/) — BleepingComputer, 2026-11-11

Tags: exchange-server, windows-server, outlook, microsoft, patches, email

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Brief generated by AI (claude-haiku-5-5) from the reporting listed under Coverage. Headlines belong to their publishers. The Morning Dev – https://themorning.dev