Microsoft announced that it has resolved Outlook sign‑in and mail‑delivery problems that affected Exchange Server environments after the October 2026 Windows Server security updates were installed.
The October security roll‑out introduced compatibility issues that prevented some users from authenticating to Outlook and caused delays in email delivery on on‑premises Exchange Server installations, a core component of many corporate messaging infrastructures.
In response, Microsoft issued a corrective update that restores normal sign‑in functionality and mail flow for affected Exchange Server systems. The fix is being distributed through the usual Windows Server update channels and can be applied by administrators alongside regular patch management procedures.
Microsoft advises organizations that have applied the October 2026 updates to promptly install the new corrective patch to avoid continued disruption. The company also reiterated its commitment to monitoring the situation and providing support to customers experiencing related issues.
Monthly security updates for Windows Server are a routine part of Microsoft’s effort to protect against emerging threats, though occasional interactions with dependent services such as Exchange can require additional remediation steps.
<small>Source: Bleeping Computer — read the original story there.</small>
