Outlook fails to start with error: 'Microsoft Outlook' exited without properly closing your Outlook data file

Sometimes After shutting down Outlook forcefully and trying to restart it, the following error is displayed:

'Microsoft Outlook' exited without properly closing your Outlook data file. 'Microsoft Outlook' must be restarted. If this error message recurs, contact support for assistance.

Outlook then exits

Solution:

• Run Process Explorer and choose "Find Handle or DLL" from the Find menu.
• Search for '.ost'. This will display all open handles to your Outlook data file.
• Choose to close all handles to your .ost file
  
• Start Outlook again
• optionally - run C:\Program Files (x86)\Microsoft Office\Office14\SCANPST.EXE