Tag: Cannot start microsoft outlook Cannot open the outlook window.

Cannot start Microsoft Outlook. Cannot open the Outlook window. The set of folders cannot be opened

| May 7, 2026

Cannot start Microsoft Outlook. Cannot open the Outlook window. The set of folders cannot be opened

This can be a snaggy error to fix. I have seen this error for years with Microsoft Exchange. Lately the fix for me has been to delete the 16,454 KB size file in the app data folder.

Usually I back up any file I delete but this one is not really a data file that works with the OST, when you set up new Outlook profile it just makes it. And this can get snagged up I believe.  If you delete it, then try reopening Outlook it might work. If not make a new profile (don’t delete the old one), set Outlook to open new profile. See if it performs better.

I also had to run 365 updates on my last client to get it working.

If not, then you might have other issues such as a VPN problem, Antivirus or Firewall.

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