Outlook - set of folders cannot be opened - unable to fix this error via any method

Anonymous
2021-11-14T11:31:50+00:00

Hello,

i have an issue i've been unable to resolve for a few weeks, maybe even months now.

I was setting up a new All-in-One PC for an employee at a company we do IT support for. The setup went without a problem, he has Windows 10 OS and a Microsoft 365 Business Standard license.
A week or two go by and he informs me hes getting the known error when opening Outlook - The set of folders cannot be opened. To simplify, I decided to create another mail profile. This seemingly resolved the issue but I get another call from him a few days later saying the same problem has occured. We repeat the process and create a 3rd email profile. The same error pops up again, even sooner (maybe a day or two). The most peculiar thing is (he has 3 or 4 profiles at this point) that if I keep swapping between the profiles randomly and trying to start Outlook, lets say 1 in 20 times it actually starts up.
So I start troubleshooting the issue with everything I could find on google.

A list of possible solutions I've tried to far:

  1. Starting outlook in safe mode - still does not start
  2. Disabling add-ins - did not help
  3. Reinstalling Office365 - did not help
  4. Repaired Office365 - did not help
  5. I believe i've tried some other repair/scan tools but nothing ammounted to anything

At this point I figured it might have to be something on his domain profile, so we delete the local profile and recreate it, the error still appears.

We replace his new PC with his older one on which everything works without any problems. We try creating a local account on his co-workers account, Outlook works fine there.

So a few days ago I decide to just reinstall the windows again hoping it would solve the issue (I did the reset with keeping the personal files). I install Outlook, it opens up. To test it out I close it down and try to re-open it - im hit with the error. I create a new profile again and manage to open Outlook exactly once, when i close it down and reopen the error hits me again. Just to make sure i repeat the process a 3rd time, same result - so in short whenever i create a new profile i manage to start up Outlook exactly once before the error appears.

At this point I'm out of ideas on what to try, I plan to bring another machine, domain join it and create his profile on it to see if the problem repeats - so far this only happens on 1 machine, on 2 others in the same domain it works fine.

Is there any reason this could be a hardware issue? Because thats the only thing that somewhat makes sense to me altho on the other hand I can't imagine it being hardware related. The OS and O365 are all updated.

Thanks for any advice or input in advance

Outlook | Windows | Classic Outlook for Windows | For home

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Anonymous
2022-02-21T18:49:57+00:00

Had the same problem

These steps fixed it.

If updating the Outlook application was not able to fix the error in Outlook “the set of folders cannot be opened” then you have to recreate the Outlook email profile. This method has helped many users to fix the error. 

  1. Go to the Windows search bar and type regedit. This will launch the Registry Editor.
  2. Then, navigate to Computer\HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Outlook\Profiles (Outlook 2019,2016)
  3. Now delete all the folders listed under Profiles.

Note: If you are using a different version of Outlook this will change as follows. Computer\HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\15.

  4. Restart the computer.

  5. Relaunch Outlook and recreate your email profile.

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  1. Anonymous
    2025-06-19T07:06:47+00:00

    what a wonderfull solution for the issues reported and 100% working foir mine

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  2. Anonymous
    2025-04-10T07:50:06+00:00

    Wow, it works for me. Thankyou

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  3. Anonymous
    2024-08-16T16:39:09+00:00

    This problem, at least for me, was easier to solve than going into regedit. It was caused when I deleted one of my email accounts and the tag specifying the default account was removed, even though I didn't delete the default account. But I didn't know that because I couldn't open Outlook to find that out.

    The fix that worked for me: (many thanks to a Microsoft support person for showing me this)

    1. Got to Control Panel. In Windows 10, from entry box on the task bar.
    2. View "large icons" from the top right drop-down.
    3. Select "Mail (Microsoft Outlook)
    4. Pick "Email Accounts"
    5. Select your preferred email account as a default.
    6. Try again to start up Outlook.

    Thanks for this advice. This simple solution worked a treat for me and seemed much better than blindly deleting a number of folders using REGEDIT. Outlook came up immediately when re-started. It was an education to know that you can address problems with the outlook Account Settings without actually starting Outlook

    Thank you so much! You just saved me...this fixed the issue for me beautifully!

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