How do you fix Cannot start Microsoft Outlook Cannot open the Outlook window the set of folders Cannot be opened?

Outlook users getting error “Cannot start Microsoft Outlook. Cannot open the Outlook window. The set of folders cannot be opened. The operation failed.” usually indicates that the outlook data file, where outlook has all the information stored cannot be opened. Before going through the steps listed below, make sure that you are not running any back up software’s that is supposed to backup the data file, because if the file is in use, then Outlook will not be able to access the file.

Secondly, make sure that the file has not been moved from it’s original location. Add-in’s can also interrupt Outlook from accessing the data file.

Method 1: Repair Corrupt System Files

Download and run Restoro to scan and repair corrupt/missing files from here, if files are found to be corrupt and missing repair them and then see if you still get the error on Outlook. If you do, then try the other method listed below.

Method 2: Reset Navigation Pane

In this solution, we will reset the navigation pane settings in Outlook. Close all applications.

1. Hold Windows key and press R. In the run dialog, type, and press Enter.
2. outlook.exe /resetnavpane
3. If Outlook starts fine, you’re good. Close and Re-open normally.
   
4. If it still won’t open after resetting the navigation pane, or if it gives an error, close/exit out of any error pop-ups and rename the Outlook.xml file to Outlook.xml.old.
5. To do this, Hold the Windows Key and Press R.  In the run dialog box type%appdata%\Microsoft\Outlook
6. and press Enter. Right-click the Outlook.xml file and choose rename, and add .old to the end of the file.
   
7. Now open Outlook to see if it works or not, if it still won’t work, then proceed with Method 2.

Method 3: Start Outlook in Safe Mode

1. Hold Windows key and press R. In the run dialog, type outlook.exe /safe and press Enter.
   
2. You will be asked which profile to use when logging in. If there is only one profile, then it will be selected by default. Click OK. If it works in Safe Mode, then the is likely to be a conflicting or corrupt add-in. Disable all add-ins and then open Outlook to confirm, if it works then enable add-in one by one until you get to the one which stops Outlook.
3. To disable add-ins, click File -> Options -> Add-ins -> COM Add-ins -> Manage -> Go
4. Uncheck all the items in Add-Ins available list and click OK. Now test.
   
5. If it still won’t work then Hold the Windows Key and Press R. Type appwiz.cpl and Click OK.
6. Locate the following programs and uninstall them.

ABBYY FineReader, Broadcom Send-to-Bluetooth Intel Send-to-Bluetooth KingSoft’s PowerWord.

Method 4: Repair Outlook Data File

Outlook stores data in data files, these files can be corrupted. Luckily, Outlook provides a tool called scanpst to scan and repair these files.

Method 5: Enabling cached exchange mode

This method is applicable to exchange users only.

1. Click Start and search for Control Panel. Go to CP, and type Mail in the search box on the top right. Click on Mail icon in the search results. In the Mail setup window, click Data Files. Select Your Account, and click Settings.
2. In advanced, check all three boxes for Use cached exchange mode, Download shared folders and Download public folder favorites. Close and Test.

Method 6: Disabling Lync at Startup

Lync is a business version of the Skype application. Often, it interferes with important elements of the Outlook application. Therefore, in this step, we will be disabling Lync at startup and open Outlook again. For that:

1. Press “Windows” + “X” keys simultaneously and select “Task Manager” from the list.
   
   Selecting Task Manager from the list
2. Click on the “Startup” tab and select the “Lync” application from the list.
   
   Clicking on the “Startup” tab
3. Click on the “Disable” button and restart your computer.
4. Start Outlook without starting Lync and check to see if the issue persists.

If nothing works, then follow Method 3 until the ost or pst file reports no errors and then add a new profile. Once done, import your ost/pst file back into Outlook. Before importing, set up your account in Outlook and if you are missing messages or contacts, then import.