Hi @Phong Võ ，
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My company user has an issue that whenever she logs into Outlook on her desktop, they create several NST files. Re-login in also happens the same situation.
Does this issue only affect the particular user in your organization? If so, it's suggested to compare the build number of her Outlook client with the other users' and see if there's any difference. I just came across the thread below and according to the discussion there, seems like there was a similar known issue months ago:
Outlook creates new NST files every time it is opened
Besides, below are some other methods which might help for your reference:
- Try opening Outlook in safe mode (Close Outlook, press Win+R, type "outlook /safe", press Enter.). This helps eliminate whether it's an issue with any add-ins.
- Create a new Outlook profile, add her account and see if the issue continues.
- Switch to Exchange Online mode. Go to File > Account Settings > Account Settings, select the account, clear the checkbox of "Use Cached Exchange Mode to download email to an Outlook data file".
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