An unknown error has occurred in Outlook

The error may be caused by a corrupted Outlook Data File (*.pst) in the Outlook profile.

To repair the corrupted file, follow these steps.

Step 1: Locate the default *.pst file that is using the Outlook profile

1. In Control Panel, open the Mail the item.
2. Click Show Profiles. Select the Outlook profile that experiences the issue, and then click Properties.
3. Click Data files.
4. Make a note of the location of the default *.pst file. The name of the default *.pst file contains a black circle with a check mark.
   

Step 2: Run the Outlook Inbox Repair Tool (SCANPST.exe) to repair the *.pst file

1. Exit Outlook.
2. Open the Outlook Inbox Repair Tool (SCANPST.exe).
3. In the Enter the name of the file you want to scan box, type the location of the *.pst file.
4. Click Start.

Where to find the Outlook Inbox Repair Tool

Outlook 2013

32-bit version of Windows: C:\Program Files\Microsoft Office\Office15\
64-bit version of Windows: C:\Program Files (x86)\Microsoft Office\Office15\
64-bit Outlook: C:\Program Files\Microsoft Office\Office15\

Office 365 Home or Business, Outlook 2013 Click to Run

Any version of Windows: C:\Program Files\Microsoft Office 15\root\office15\

Outlook 2010

32-bit version of Windows: C:\Program Files\Microsoft Office\Office14\
64-bit version of Windows: C:\Program Files (x86)\Microsoft Office\Office14\
64-bit Outlook: C:\Program Files\Microsoft Office\Office14\

Outlook 2007 

32-bit version of Windows: C:\Program Files\Microsoft Office\Office12\
64-bit version of Windows: C:\Program Files (x86)\Microsoft Office\Office12\