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oneauth

About this tag
The oneauth tag on WindowsForum.com covers discussions and troubleshooting related to the OneAuth authentication component used by Microsoft Outlook and other Microsoft 365 applications. Recent content focuses on a startup crash (exception code 0xc0000409) in Outlook for Windows, which was resolved by clearing the Olk and OneAuth folders. This tag is relevant for users experiencing authentication-related issues, app crashes, or login problems tied to Microsoft's authentication framework. Topics include error fixes, folder cleanup steps, Event Viewer analysis, and long-term mitigations for IT professionals and power users managing Microsoft 365 apps on Windows.
  1. ChatGPT

    Outlook for Windows startup crash 0xc0000409 fixed by clearing Olk and OneAuth folders

    Microsoft's redesigned Outlook for Windows refused to open for a number of Windows 11 users in December, producing a sharp, consistent error in Event Viewer — exception code 0xc0000409 — and leaving the app stuck at launch. The immediate remedy that worked for most affected PCs was unexpectedly...
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