Microsoft has identified problems with this month’s Windows Server security updates that are disrupting Exchange Server operations. The company confirmed that users on Windows Server 2019 and later versions are experiencing difficulties signing into Outlook on the web and receiving email after installing the October updates. Some affected systems display specific error messages and event logs indicating mailbox access failures.
Microsoft attributes the issues to a new default memory limit on Endpoint Mapper that restricts simultaneous lookup calls to 512, which proves insufficient during heavy Exchange Server usage. While the company works on a permanent solution, it has released a temporary workaround involving a registry modification that administrators can apply to affected systems. Microsoft clarified that the problems are not caused by Exchange Server security updates themselves and advised customers against uninstalling the Windows Server updates.
Source: Read the full story at BleepingComputer
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