The bug causes the Outlook window to become unresponsive and show the “Not Responding” status.
The issue is affecting Windows 11 and Windows 10 systems, Microsoft has confirmed
Photo Credit: Microsoft
Microsoft has issued an advisory regarding the latest Windows security update after widespread reports of bugs and system issues linked to the patch surfaced. The update, released on January 13, resulted in Windows users with Outlook POP account profiles encountering issues, such as the page becoming unresponsive. The Redmond-based tech giant has advised users to uninstall the update until a more stable build of the Windows security update is rolled out.
On a support page, Microsoft said that Classic Outlook can hang or freeze entirely after installing the Windows 11 update version KB5074109. This issue primarily affects classic Outlook profiles that rely on POP (Post Office Protocol) accounts or that store PST (Personal Storage Table) files in locations synced with cloud services like OneDrive.
As per the company, the bug causes the Outlook window to become unresponsive and show the “Not Responding” status, requiring users to force-close the app or restart their PC to regain access.
In some cases, the process remains active in the background unless terminated via Task Manager or a system restart is performed. Reports also indicate that emails may not appear in the Sent Items folder or that items begin re-downloading unexpectedly, which is also believed to be a side effect of how PST files are handled post-update.
As per Microsoft, the problem affects Windows 11 versions including 24H2 and 25H2 that received the KB5074109 update, and similar behaviour has been observed on some Windows 10 systems that were updated around the same time.
The KB5074109 update can automatically get installed onto PCs since it is a mandatory update until the Windows Update service is manually paused. The tech giant, however, is yet to roll out a fix. Until it is available, it has advised users to use webmail instead, as other workarounds, such as moving PST files out of OneDrive-synced folders, “may be complicated”.
If they are experiencing significant issues, then affected users are recommended to remove KB5074109 and pause updates temporarily to prevent it from reinstalling while the company works on a patch.
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