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Microsoft classic Outlook freezes and hangs after KB5074109 Windows 11 update

Service Disruption
First reported
Last updated
Happening score
H score 13
1 unique sources, 2 articles

Summary

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The classic Outlook desktop client is freezing and hanging for POP email users after the KB5074109 Windows 11 security update, with some users unable to reopen Outlook unless they end the process in Task Manager or restart the device. Microsoft says the issue can also affect Windows 10 and Windows Server 2025/2022/2019, especially when PST files are stored in OneDrive or other cloud-backed storage, and it has provided a temporary workaround while the issue remains under investigation.

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Timeline

  1. 21.01.2026 17:12 1 articles · 4mo ago

    Microsoft issues temporary workaround for Outlook freezes

    Mitigation Patch Update

    Microsoft issued a temporary workaround for the classic Outlook desktop client freezing after the KB5074109 Windows 11 security update on Windows 11 25H2 and 24H2, with guidance to use webmail, move Outlook PST files out of OneDrive, or uninstall KB5074109 or KB5073724 until a permanent fix is available. Microsoft also said the issue can affect Windows 10 and Windows Server platforms when Outlook stores PST files in cloud-backed storage such as OneDrive or Dropbox.

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  2. 16.01.2026 14:12 1 articles · 4mo ago

    KB5074109 breaks classic Outlook for POP users

    Victim Impact Update

    A January 14, 2026 Windows 11 security update, KB5074109, begins causing the classic Outlook desktop client to freeze, crash, fail to exit properly, and refuse to restart for users with POP email accounts on Windows 11 25H2 and 24H2.

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  3. 16.01.2026 14:12 2 articles · 4mo ago

    Microsoft investigates KB5074109 Outlook freeze issue

    Initial Disclosure

    Microsoft says the KB5074109 issue is an emerging problem affecting the classic Outlook desktop client for POP users on Windows 11 25H2 and 24H2, and the Outlook and Windows teams are investigating while advising affected users to uninstall KB5074109 through Settings > Windows Update > Update history > Uninstall updates until a permanent fix is available.

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