Many people use Outlook as their preferred email client, but sometimes certain errors can appear. The set of folders cannot be open is one of those errors, and it will prevent you from starting Outlook.

The iCloud app can interfere with the Outlook and give you this error

  • Outlook is as popular as an email client can get, and many use it as a preferred solution for professional communication.

  • But issues may occasionally occur and The set of folders that cannot be opened is a particularly grave one since it prevents you from starting the app altogether.

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Even though this is an annoying error, you should be able to fix it by using one of the following solutions.

Why the set of folders cannot be opened in shared calendar?

File corruption is a common problem in Outlook, and many reported that The folder cannot be expanded. This happens if your profile or installation is damaged.

  • Why the set of folders cannot be opened in shared calendar?
  • Fix Microsoft Outlook error: The set of folders cannot be opened
    1. Create a new Outlook profile
    1. Use Taskbar shortcut to start Outlook
    1. Be sure to use a separate password for Outlook
    1. Sign out of iCloud
    1. Reinstall iCloud
    1. Don’t install Exchange Server Cumulative Update
    1. Make sure to install 64-bit version of Office
    1. Remove the user from delegates and add them back again
    1. Use Outlook Tools
    1. Make sure that your .pst file is on the C drive
    1. Delete your account from the Mail app
    1. Don’t use the X button to close Outlook
    1. Export your profile from the registry
    1. Remove Evernote
    1. Remove .xml files from the Outlook directory
    1. Use only one Exchange account
    1. Use scanpst.exe to fix your .ost file
    1. Use Google’s DNS
    1. Run Outlook as administrator and turn off the Compatibility mode
    1. Reinstall Outlook and remove its values from the registry
    1. Use Microsoft Support and Recovery Assistant
    1. Repair your Office installation
    1. Set a different default account
    1. Clean Microsoft Office credentials
    1. Start Outlook in safe mode
    1. Remove Outlook account and remove its files
    1. Stop all Outlook processes running in the background
    1. Use /resetnavpane parameter
    1. Close the Lync application
    1. Make sure that the path to the .pst file is correct
    1. Enable IPv6
    1. Enable Use cached exchange mode
    1. Delete the Outlook key from your registry
    1. Change the value of AllowUnregisteredMapiServices DWORD

In some instances, new folders aren’t visible in Outlook, and if that happens, you might want to try recreating them.

This problem can also appear if one or more folders in your mailbox are named incorrectly, so be sure to check that as well.

Fix Microsoft Outlook error: The set of folders cannot be opened

1. Create a new Outlook profile

If you’re frequently getting The set of folders cannot be opened error, you might be able to solve it simply by creating a new Outlook profile. To do that, you just need to follow these simple steps:

  • Open Control Panel. To do that, press Windows Key + S and enter the Control Panel. Now choose Control Panel from the list of results.
  • Navigate to the Mail section. If you can’t find it, go to User Accounts > Mail.
  • Now click the Show Profiles button.
  • Select your profile and click on Remove.
  • In Mail Profiles window click the Add button and enter the name of your new Outlook profile. Click OK to save changes.
  • Now choose Auto Account Setup or Manual Setup and follow the instructions on the screen to complete the process.

If your Outlook profile is corrupted, you can fix it by following this simple guide.

After you create a new Outlook account the problem should be resolved and Outlook will start working without any problems. Few users claim that you don’t have to create a new profile from the Mail section.

Instead, you just have to remove all profiles, start Outlook and you’ll be asked to create a new profile.

If you have multiple accounts, you can remove them all and then add them one by one until you find the one that is causing this issue.

2. Use Taskbar shortcut to start Outlook

Many users tend to pin the most used applications to their Taskbar in order to launch them quickly. According to users, you can avoid The set of folders cannot be opened error message simply by starting Outlook using its Taskbar shortcut.

To do that, follow these steps:

  • Make sure that Outlook is pinned to your Taskbar. If not, locate the Outlook shortcut and drag it to your Taskbar.
  • Locate the Outlook shortcut on your Taskbar and right-click it. Choose the New E-mail message or Outlook 2016 option from the menu.

After doing that, Outlook should start without any problems or error messages. Keep in mind that this is just a workaround, so you’ll have to repeat this solution every time you want to start Outlook.

3. Be sure to use a separate password for Outlook

According to users, The set of folders cannot be opened error appears if you’re using two-step verification for your Gmail account.

Two-step verification is one of the best ways to protect your email account from unauthorized access, but sometimes problems with it can occur.

If you’re having this problem in Outlook, be sure to use a separate password for Outlook and check if that solves the problem.

4. Sign out of iCloud

Several users reported that The set of folders cannot be opened error appears while using iCloud with Outlook. To fix the problem, you just need to sign out and sign back into iCloud.

This is rather simple and you can do it by following these steps:

  • Be sure to completely close Outlook.
  • Now start iCloud. You can do that by opening the Start Menu and typing iCloud. Choose the iCloud Desktop app from the list of results.
  • When iCloud opens, click on the Sign out button.
  • You’ll be asked whether you want to keep your contacts, calendar, and tasks. Choose Delete from computer option.
  • After deleting your contacts wait for a few minutes for changes to take effect.
  • Now sign in to iCloud again.
  • Once you sign in, choose the option to sync Mail, Contacts, Calendars, and Tasks.

After doing that, Outlook should start again and you won’t have any problems with it.

5. Reinstall iCloud

iCloud has some issues with Outlook that can cause The set of folders cannot be opened error message to appear.

According to users, you need to reinstall iCloud completely in order to fix this problem. This is relatively simple and you can do it by following these steps:

  • Open Outlook and go to File > Account Settings > Account Settings > Data Files.
  • Locate the iCloud data file and click on Remove. You can easily recognize iCloud data file by its .aplzod extension. When the confirmation message appears, confirm that you want to delete the data file.
  • After doing that, close Outlook.
  • Now open iCloud Control Panel and uncheck Mail, Contacts, Calendars, and Tasks with Outlook options.
  • Download and install the latest version of iCloud. During the installation be sure to select the Repair option.
  • After you install iCloud again, restart your PC.
  • Once your PC restarts, start iCloud Control Panel and select Mail, Contacts, Calendars, and Tasks with Outlook, and start the sync process.

After doing that, start Outlook again and check if the error message still appears. Few users claim that you don’t have to reinstall iCloud to fix this problem. According to them, you just have to repair your iCloud installation to fix this error.

If you want to download iCloud Control Panel on Windows 10, take a look at this awesome article and do it with ease.

6. Don’t install Exchange Server Cumulative Update

Several users reported The set of folders cannot be opened error message after installing Exchange Server Cumulative Update. If you’re having this problem, remove this update and check if that solves the issue.

7. Make sure to install 64-bit version of Office

According to users, The set of folders cannot be opened error can appear if you’re using a 32-bit version of Microsoft Office. If you’re using a 64-bit version of Windows, we strongly advise you to reinstall Office and install the 64-bit version instead.

The 64-bit version offers better performance on 64-bit systems, so there’s no reason not to install it. Users reported that they successfully solved the problem after installing the 64-bit version of Office, so be sure to try that.

8. Remove the user from delegates and add them back again

This error message can sometimes appear while using a shared mailbox. To fix the issue, users are suggesting removing users from delegates or permission-level access and adding them back again.

After doing that you just have to restart Outlook and the problem should be resolved completely.

9. Use Outlook Tools

If you’re getting The set of folders cannot be opened error message in Outlook, you might be able to fix it using Outlook Tools. This is a third-party tool, but it can help you fix this problem. To use this tool, just follow these steps:

  • Download and install the latest version of Outlook Tools.
  • After doing that, start Outlook Tools and navigate to Start-up Switches.
  • In the column on the left click on Profiles and then click on Start Outlook.
  • Now you should see Choose Profile panel. Click on New and enter the name for your profile.
  • Now click on Options and check Set as default profile. Click OK to save changes.
  • Now enter the necessary profile information such as your email address and password.
  • If everything is in order, Outlook will set up your email and create your profile automatically. After the process is completed, click on Finish.

After doing that, Outlook should start automatically without any errors.

10. Make sure that your .pst file is on the C drive

Several users claim that The set of folders cannot be opened error appears because the .pst file is located on a drive other than C. According to them, moving the .pst file to the C drive fixed the problem for them, so be sure to try that.

To fix the issue, you need to move your .pst file to any directory on your C drive and select it from Outlook’s configuration window.

This is a strange solution, but a few users claim that it works for them, so be sure to try it out.

11. Delete your account from the Mail app

Windows 10 already comes with a built-in email client called Mail. This is a solid email application, but many users prefer something more advanced.

According to users, The set of folders cannot be opened error can appear if you have added your email account to the Mail prior to adding it to Outlook.

This is a strange bug, but you can fix it simply by removing your email account from the Mail application. To do that, you need to follow these simple steps:

  • Open the Mail app.
  • Now navigate to the Accounts section in the left pane.
  • Manage Account pane will now appear. Select your email account from it.
  • When the Account settings window appears, click on Delete account.
  • The confirmation message will now appear. Click on Delete to remove your account.

After you remove your email account from the Mail app, you should be able to start Outlook without any problems. We don’t know why this problem occurs, but if you’re using the Mail app, remove your email account from it and check if that solves the issue.

12. Don’t use the X button to close Outlook

This is just a workaround, but it works according to users. Many users reported that they are unable to start Outlook due to The set of folders cannot be opened error.

According to users, this problem appears because you’re using the X button to close Outlook. We’re not sure how this affects Outlook, but users have come up with a workaround.

To prevent this message from appearing, be sure to close Outlook by clicking File > Exit. By doing that you should be able to start it without any errors. This is a simple workaround, and users claim that it works, so we encourage you to try it out.

13. Export your profile from the registry

Several users reported The set of folders cannot be opened error message after upgrading from Office 2013 to Office 2016. According to them, they were unable to set their profile in Outlook due to this error.

However, users found a way to export their Outlook 2013 profile using Registry Editor. To do that, you need to follow these steps:

  • Press Windows Key + R and enter regedit. Press Enter or click OK.
  • In the left pane, navigate to the  key:
  • HKEY_CURRENT_USERSOFTWAREMicrosoftOffice15.0OutlookProfiles
  • Right-click the Profiles key and choose Export from the menu.
  • Choose a safe location for your file, set profile.reg as the name, and click on Save.
  • Now locate profile.reg file, right-click it and choose Edit from the menu.
  • When Notepad opens, replace 15.0 with 16.0 everywhere in the file. To do this automatically, just press Ctrl + H and enter 15.0 in Find what and 16.0 in Replace with field. Now click the Replace All button.
  • After doing that, save changes.
  • Now locate profile.reg and run it.
  • The confirmation message will now appear. Click Yes to proceed.

After doing that, your profile will be added to Outlook and you should be able to use it without any problems. Keep in mind that this is an advanced solution, so if you’re not comfortable editing your registry, you might want to skip this solution entirely.

HKEY_CURRENT_USERSOFTWAREMicrosoftOffice15.0OutlookProfiles

Right-click the Profiles key and choose Export from the menu.

If you can’t edit your Windows 10’s registry, read this handy guide and find the quickest solutions to the issue.

14. Remove Evernote

Evernote is a great note-taking app but sometimes this app can be related to The set of folders cannot be opened error. Evernote will sometimes interfere with Outlook and cause this error to appear.

To fix the issue, users are suggested to uninstall Evernote from their PC.

If that solves the problem, you might want to install the latest version of Evernote and check if the issue still persists.

15. Remove .xml files from the Outlook directory

According to users, The set of folders cannot be opened error can appear due to XML files in Outlook’s directory. These files can become corrupted causing the problem to appear.

To fix the issue, you need to delete those files manually. Removing these files won’t cause any problems since Outlook will recreate them, so there’s no need to worry.

To fix the problem, you need to do the following:

  • Press Windows Key + R and enter appdata. Press Enter or click OK.
  • When AppData directory opens, navigate to LocalMicrosoftOutlook16*.
  • Now locate and remove all .xml files.

After doing that, try to start Outlook again. Users reported that removing .xml files fixed the problem for them, so be sure to try it out.

In our solution, we showed you how to fix the problem in Outlook 2016, but the approach should be the same for older versions of Outlook.

16. Use only one Exchange account

The set of folders cannot be opened error message can appear in Outlook if you’re using two or more Exchange accounts. This is a strange bug, and as a workaround, users are suggesting using only one Exchange account at a time.

According to them, you can use permissions to access the second account, but if you add two or more accounts, the error message will appear. This is a strange bug, but hopefully, Microsoft fixed it by now.

17. Use scanpst.exe to fix your .ost file

Users reported that The set of folders cannot be opened error can appear if your .ost file is corrupted.

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To fix the problem, you need to use Microsoft Outlook Inbox Repair Tool also known as scanpst.exe. To do that, follow these steps:

  • Open your Office Installation directory. By default, it should be
  • C:Program Files(x86)MicrosoftOfficeOffice16.
  • Now locate scanpst.exe and run it.
  • When Microsoft Outlook Inbox Repair Tool starts, click on Browse.
  • Now you need to select your .ost or .pst file. You can find the .ost file in this directory:
  • C:Usersyour_usernameMyDocumentsOutlookFiles
  • As for .pst file, it is located in
  • C:Usersyour_usernameAppDataLocalMicrosoftOutlook. You can use any of these files for the repair process.
  • Once you select the desired file click the Start button to scan it.
  • When the scan is completed, you’ll be asked whether you want to repair the file. Click the Repair button. Keep in mind that you might need to run the repair process a couple of times if you want to completely fix all errors.

After you repair your .ost file, the error message should disappear and you’ll be able to use Outlook without any problems.

C:Program Files(x86)MicrosoftOfficeOffice16.

C:Usersyour_usernameMyDocumentsOutlookFiles

As for .pst file, it is located in

C:Usersyour_usernameAppDataLocalMicrosoftOutlook. You can use any of these files for the repair process.

18. Use Google’s DNS

The set of folders cannot be opened error can sometimes appear due to your DNS configuration.

Most users use their default DNS that is provided by their ISP, but if you have this problem on your PC, you might want to switch to Google’s DNS instead. To do that, follow these steps:

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  • Open Control Panel and go to Network and Sharing Center.
  • In the left pane, click on Change adapter settings.
  • Network Connections window will now appear. Locate your connection, right-click it, and choose Properties from the menu.
  • When the Properties window opens, select Internet Protocol Version 4 (TCP/IPv4) and click on Properties.
  • Select Use the following DNS server addresses option and set Preferred DNS server to 8.8.8.8 and Alternate DNS server to 8.8.4.4. Click OK to save changes.

If the DNS server is not responding in Windows 10, you can fix it by following the simple steps from this article.

After you set your DNS, you just need to flush it to complete the process. To do that, follow these steps:

  • Press Windows Key + X to open Win + X menu and choose Command Prompt (Admin). If Command Prompt isn’t available, you can also use PowerShell instead.
  • When Command Prompt starts, enter ipconfig /flushdns command and press Enter to run it.

After doing that, your DNS will be changed and any problems with Outlook should be resolved completely.

If you’re having trouble accessing Command Prompt as an admin, then you better take a closer look at this guide.

19. Run Outlook as administrator and turn off the Compatibility mode

Few users claim that you can fix The set of folders cannot be opened error simply by starting Outlook as an administrator. The same users also claim that this problem is caused by Compatibility mode, so be sure that you don’t use it for Outlook.

To change these settings, you need to do the following:

  • Locate Outlook’s shortcut, right-click it, and choose Properties from the menu.
  • Go to the Compatibility tab and uncheck Run this program in compatibility mode for option. Now check Run this program as an administrator option and click on Apply and OK to save changes.

After making these changes, try to start Outlook again and check if the error message appears again.

Several users claim that turning on Compatibility mode fixed the problem for them, so if you have this option disabled, be sure to enable it and check if it solves the issue.

Does nothing happen when you click on Run as administrator? Don’t worry, we’ve got the right fix for you.

20. Reinstall Outlook and remove its values from the registry

If you’re getting The set of folders cannot be opened error while trying to run Outlook, you might be able to fix it by reinstalling Office. To do this, first, you need to uninstall Office from your PC.

After you remove Office, restart your PC to finish the uninstall process. Keep in mind that Outlook will leave certain registry entries behind once you remove them, so you’ll need to remove them manually. To do that, follow these steps:

  • Open Registry Editor. For more instructions on how to do that, check Solution 13.
  • When Registry Editor opens, In the left pane navigate to
  • HKEY_CURRENT_USERSoftwareMicrosoftOffice
  • Right-click the Office key and choose Delete from the menu.
  • When the confirmation dialog appears, click on Yes.
  • After doing that, restart your PC.

When your PC restarts, Outlook should be completely removed. Now you just have to reinstall Microsoft Office and the problem should be fixed.

HKEY_CURRENT_USERSoftwareMicrosoftOffice

Right-click the Office key and choose Delete from the menu.

If you want to completely and safely uninstall an app on Windows 10, we recommend you try a dedicated uninstaller tool.

21. Use Microsoft Support and Recovery Assistant

This error message can be quite annoying and it can prevent you from starting Outlook. However, you might be able to fix the problem by downloading Microsoft Support and Recovery Assistant.

According to Microsoft, this tool can fix various Outlook problems, and several users claim that it fixed this issue for them. The tool is completely free and simple to use, so be sure to try it.

22. Repair your Office installation

If The set of folders cannot be opened error message appears constantly, you might be able to fix it by repairing your Office installation.

Sometimes your installation can become corrupted, and to fix the problem you need to repair it by following these steps:

  • Open Control Panel and navigate to Programs and Features.
  • When Programs and Features window opens, select Microsoft Office from the list of applications and click the Change button at the top.
  • Now select Quick Repair option.
  • Follow the instructions on the screen to complete the repair.

After you repair your Office installation, the problem should be resolved and everything should work normally.

23. Set a different default account

Several users claim that they fixed this error simply by selecting a different default account. If you have only one email account assigned to Outlook, this solution won’t work for you, so you should probably skip it.

If you have multiple email accounts assigned to Outlook, you might be able to fix the problem by selecting a different default account. To do that, follow these steps:

  • Open Control Panel and go to Mail > Email accounts.
  • You should now see all your available email accounts. Set a different account as the default one and save changes.
  • After doing that, try to access Outlook again. Keep in mind that you might have to set a default account a couple of times before you find the one that works.

This is a strange workaround, but it works according to users, so be sure to try it out if you have multiple accounts added to Outlook.

24. Clean Microsoft Office credentials

According to users, you can fix The set of folders cannot be opened error simply by removing Microsoft Office credentials from the Credential Manager.

Credentials Manager holds all your local passwords, and to fix the problem, you need to remove credentials for Microsoft Office. To do that, just follow these steps:

  • Press Windows Key + S and enter credential. Select Credential Manager from the list of results.
  • When Credential Manager opens, click on Windows Credentials.
  • Locate Outlook or Microsoft Office in the list of credentials and click it.
  • Now choose Remove to remove credentials from your PC.
  • Confirmation message will now appear. Click on Yes to remove the credentials.

After you remove the credentials, the problem should be resolved and you’ll be able to use Outlook without any problems.

25. Start Outlook in safe mode

Few users claim that you can fix this problem simply by starting Outlook in Safe mode. Outlook also uses various add-ins, and in order to fix the problem, you might have to disable them.

This is relatively simple and you can do it by following these steps:

  • Press Windows Key + R and enter Outlook /safe. Press Enter or click OK.
  • If Outlook starts in safe mode, you need to disable your add-ins. To do that, click on File > Options > Add-ins.
  • Now click on the Go button next to Manage: Com-in Add.
  • Disable all available add-ins and click OKto save changes.

After disabling add-ins, try to start Outlook again and check if the problem still appears. Users reported that LABBYY FineReader add-in was the cause for this problem, so if you have it, be sure to disable it and check if that solves the issue.

Most Windows users don’t know how easy it is to add Safe Mode to the boot menu. Find out how you can do it in just a couple of steps.

26. Remove Outlook account and remove its files

The set of folders cannot be opened error can appear due to problems with your Outlook profile. To fix the issue, users are suggesting removing your profile and its .ost file. This is relatively simple and you can do it by following these steps:

  • Remove your Outlook.com email account.
  • After doing that, you need to remove its .ost file. To do that, navigate to
  • C:Usersyour_usernameAppDataLocalMicrosoftOutlook
  • directory, locate the .ost file and delete it.
  • After doing that, recreate your Outlook email account.

This is a simple solution, and a few users reported that it worked for them, so be sure to try it out. Several users claim that you can perform this solution without removing your email account.

C:Usersyour_usernameAppDataLocalMicrosoftOutlook

directory, locate the .ost file and delete it.

According to them, you just have to delete the .ost file associated with your account, and Outlook will recreate it automatically.

Some users are also recommending deleting all .ost files since it’s possible that some other email account is causing this problem.

27. Stop all Outlook processes running in the background

According to users, this problem can appear if the Outlook process is running in the background.

Due to certain errors, Outlook might be running in the background without your knowledge, and that can cause The set of folders cannot be opened error to appear.

To fix the issue, you need to end the Outlook process using Task Manager. To do that, follow these steps:

  • Open Task Manager. You can do that quickly by pressing Ctrl + Shift + Esc on your keyboard.
  • When Task Manager opens, look for Outlook in the Processes tab. If you can’t find it, go to the Details tab and look for the Outlook process. Once you locate the process, right-click it, and choose End Task from the menu.

Keep in mind that this is just a workaround, so you’ll have to repeat it every time the problem occurs.

Can’t open Task Manager? Don’t worry, we’ve got the right solution for you.

28. Use /resetnavpane parameter

A few users reported that they managed to fix the problem simply by using /resetnavpane parameter. It seems that the problem was caused by the navigation pane in Outlook, and that caused this problem to occur.

To fix it, you need to reset your navigation pane by following these steps:

  • Press Windows Key + R to open the Run dialog.
  • When the Run dialog opens, enter Outlook.exe /resetnavpane command. Press Enter or click OK to run it.

Once you run this command your navigation pane will reset to default and hopefully, the problem will be fixed.

29. Close the Lync application

According to users, third-party apps can interfere with Outlook and cause The set of folders cannot be opened error. Several users concluded that the cause for this error is the Lync application.

To fix the problem, you need to close this application and check if that solves the issue. If the problem still persists, you might have to uninstall Lync to fix the problem.

30. Make sure that the path to the .pst file is correct

Many users reported this problem because the path to their .pst file isn’t correct. Some users prefer to save this file in a different location, and that can cause the problem to appear.

To fix the issue, you need to navigate to Mail settings in Control Panel and set the correct path to your .pst files. After doing that, the problem should be resolved and you’ll be able to use Outlook without any problems.

31. Enable IPv6

According to users, The set of folders cannot be opened error can appear if IPv6 isn’t enabled for your network connection. To fix the problem, you need to enable it by following these steps:

  • Navigate to Network and Sharing Center and open your connection’s properties window. For more instructions on how to do that, check Solution 18.
  • When the Properties window opens, locate Internet Protocol Version 6 (TCP/IPv6) and check it. Now click OK to save changes.

Once you enable IPv6 the problem should disappear.

32. Enable Use cached exchange mode

According to users, you might be able to fix the problem simply by enabling the Use cached exchange mode feature. To enable this option, just follow these steps:

  • Go to Control Panel > Mail > Email accounts.
  • Select the problematic account and click on Change.
  • Now navigate to the Offline settings and check Use cached exchange mode.

After enabling this feature, the problem should be resolved, and you’ll be able to use Outlook without any problems. A few users are suggesting enabling Download shared folders and Download public folder options as well, so you might also want to try that.

33. Delete the Outlook key from your registry

According to users, The set of folders cannot be opened error can appear if your Outlook key is damaged. To fix the problem, you need to open Registry Editor and delete the problematic key. To do that, follow these steps:

  • Open Registry Editor.
  • In the left pane, navigate to this key
  • HKEY_CURRENT_USERSoftwareMicrosoftOffice15.0OutlookProfilesOutlook
  • Keep in mind that this key can sometimes be called Default Outlook Profile instead.
  • Right-click the Outlook key and choose Delete from the menu. When the confirmation message appears, click on Yes.
  • Now right-click the Profiles key and choose New > Key from the menu. Enter Outlook as the name of the new key.

After doing that, you just need to start Outlook again and the problem should be resolved completely.

HKEY_CURRENT_USERSoftwareMicrosoftOffice15.0OutlookProfilesOutlook

Keep in mind that this key can sometimes be called Default Outlook Profile instead.

If you want to prevent access to registry editing tools in Windows 10, check out this dedicated guide that will help you do that.

34. Change the value of AllowUnregisteredMapiServices DWORD

Few users claim that this problem occurs due to AllowUnregisteredMapiServices DWORD in your registry. Apparently, there’s a problem with this DWORD and iCloud service that causes the error to appear.

To fix it, you need to open Registry Editor and modify this key. You can do that by following these steps:

  • Open Registry Editor.
  • In the left pane, navigate to
  • HKEY_CURRENT_USERSoftwareMicrosoftOffice12.0OutlookSecurity
  • This key might be slightly different depending on the version of Outlook that you’re using.
  • Once you navigate to the Security key, in the right pane look for AllowUnregisteredMapiServices DWORD. Double click AllowUnregisteredMapiServices DWORD to open its properties and set its Value data to 1. Click OK to save changes.

If you don’t have this key and DWORD available in your registry, you might have to create them manually and then edit them. Modifying the registry is an advanced procedure, so if you’re not comfortable with it, you might want to skip this solution.

HKEY_CURRENT_USERSoftwareMicrosoftOffice12.0OutlookSecurity

This key might be slightly different depending on the version of Outlook that you’re using.

The set of folders cannot be opened error can prevent you from using Outlook, but you should be able to fix this problem by using one of our solutions.

If any of the emails are damaged in Outlook, you can just fix them quickly using Repair Toolbox for Outlook. It’s a great tool that repairs all your emails together with all their contents.

For any other suggestions or questions, don’t hesitate to leave them in the comments section below and we’ll be sure to check them out.

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