How to fix “Unable to open your default e-mail folders” when you open Outlook

This issue occurs when Outlook is installed in a compatibility mode or if default profile used by Outlook gets corrupted during upgrade\downgrade.

Follow the instructions below to fix this issue:

Solution 1: Check if Outlook is in Compatibility mode:

• Right click on Outlook.exe icon > Click on Properties > Click on Compatibility tab   
• If there are any check boxes marked > unmark them

Solution 2: Delete\Rename the *.ost file

(*.ost it’s a local Exchange cached mode file usually with the name outlook.ost)

• Open Outlook folder by following this location:
• C:\Users\username\AppData\Local\Microsoft\Outlook (Windows 7)
• C:\Documents and Settings\username\Local Settings\Application Data\Microsoft\Outlook (Windows Xp)
• Delete\Rename the users *.ost file
• Reconfigure user’s email profile.