How to fix Outlook won't open 'set of folder cannot be opened' error on Windows 11, 10

To fix Outlook when it’s not opening on Windows 11 or 10, delete the “Outlook” Registry key on “HKCU\SOFTWARE\Microsoft\Office\16.0\Outlook\Profiles,” and recreate the app email profile.

On Windows 11, if you cannot open the desktop version of Outlook, it’s possible to resolve this problem quickly through the Registry, and in this guide, I’ll explain the steps to complete this process.

If you have been trying to launch the Outlook app from the suite of Office 2021, 2016, or 2016 apps, but it won’t open with the error “Cannot start Microsoft Outlook. Cannot open the Outlook window. The set of folders cannot be opened. The attempt to log on to Microsoft Exchange has failed” message, then you will have to recreate the email profile.

You can accomplish this by deleting the Registry key containing the profiles, allowing you to relaunch the Outlook app to set up the account again.

In this guide, I’ll outline the steps to repair the Outlook app when it doesn’t start on Windows 11 (or 10).

Warning: It’s crucial to note that modifying the Registry can cause serious problems if not used properly. It’s assumed you know what you’re doing and created a full backup of your system before proceeding. Also, this process may delete previously downloaded emails and data, so after completing the steps, resync may be necessary.

Fix error preventing Outlook app from opening

To fix the error “set of folder cannot be opened,” close Outlook 2021, 2016, or 2016, and use these steps:

Open Start on Windows 11 (or 10).
Search for regedit and click the top result to open the Registry.
Navigate to the following path:
```
HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Outlook\Profiles
```
Quick note: In the older versions of the email client, you may need to use the “HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\15” path.
Right-click the Outlook key (folder) and choose the Delete option.

Quick note: This action will delete the profiles associated with the Outlook app, but if you get the error in question, it’ll probably be empty.
Click the Yes button.

Once you complete the steps, you should be able to relaunch the Outlook app to recreate the email profile and reconnect your email accounts to access your emails.