Fix: The Set of Folders Cannot Be Opened Error on Windows 10

It is reported that Outlook users encounter the error “Cannot start Microsoft outlook. Cannot open the Outlook window. The set of folders cannot be opened”. Usually, this error indicates the Outlook data file that stores all the information of Outlook cannot be opened.

Before you perform the following fixes, you need to do that:

  • Turn off all backup software like iCloud that is supposed to back up the data file. This is because Outlook won’t be able to access the file if the file is in use.

Now, let’s begin to fix the “cannot start Microsoft outlook the set of folders cannot be opened” error.

Fix 1. Create a New Outlook Profile

If your Outlook profile gets corrupted or damaged, the set of folders cannot be opened error may happen to you frequently. You can resolve it entirely by creating a new Outlook profile. Here’s a full guide.

Step 2. Change the View by to Large icons, and then click User Accounts in all listed items.

Step 3. Click Mail > Show Profiles buttons one by one.

Step 4. Select your profile and click the Remove button.

Step 6. Click OK to save this change. After that, you can select the Auto Account Setup or Manual Setup, and then you can follow the on-screen instructions to complete the process.

Now, you can check if the cannot start Microsoft Outlook error is resolved.

The navigation pane stores all the folders of your Outlook data and icons like Contacts, Tasks, Calendar and etc. Resetting the navigation pane parameter will remove all the folders, but it can resolve the “cannot open the Outlook window” error as well.

Here’s how:

Step 1. Close all the applications related to Outlook.

Step 2. Press Win + R keys to open the Run box, and then type outlook.exe /resetnavpane in it and hit Enter.

If you can open Outlook normally after running the command, that’s good. If not, you can try the following steps.

Step 1. Open the Run box, and then type the %appdata%\Microsoft\Outlook command and hit Enter.

Step 3. Reopen Outlook to see if it can work. If this method fails, move on to the next methods.

Fix 3. Run Outlook in Safe Mode

Many users reported that they fixed the error simply by starting Outlook in Safe Mode. This is because Outlook will start without loading the Add-ins in Safe Mode. To run Outlook in Safe Mode, you need to do:

Step 1. Press Win + R keys to open the Run box, and then type Outlook /safe in it and hit Enter.

If Outlook can run in Safe Mode fine, you need to disable all the Add-ins. You can follow the steps below.

Step 2. At the bottom of the window, select COM Add-ins in the Manage box and click the Go button.

Step 3. Then you will see a list of Add-ins, disable all of them and click OK.

Step 4. Restart Outlook and check if the set of folders cannot be opened error still persists.

Fix 4. Repair Outlook Data Files

Outlook data files contain all the data like email messages, tasks, and events. If these files get corrupted or damaged due to various reasons, you may encounter the vexing error. You can run the inbox repair tool of Outlook that will scan and repair the corrupted files. More detailed steps you can read this article.

Fix 5. Disable the Lync Application at Startup

Sometimes third-party software can also interrupt Outlook and cause the error. According to the user’s report, the Lync application, a business version of Skype can cause the error. Thus, we recommend that you disable the Lync application.

Step 2. Go to the Startup tab, and then select the Lync application from the list and click the Disable button at the bottom.

Step 3. Restart your computer and start Outlook to check if the error is fixed.

Originally published at on November 24, 2019.