How do I rebuild the outlook 2011 for mac email database?

Rebuild the database

1. Quit all applications.
2. Hold down the Option key on the keyboard, and then start Outlook 2011. 
   
   Note You can also browse to the Database Utility by opening the Application folder and then opening the Microsoft Office 2011 folder. Open the Office folder, and then double-click Microsoft Database Utility.app.
3. In the Database Utility window, select the database that you want to maintain, and then click Rebuild.
4. The Rebuilding Main Identify window will open and show the progress. When the operation is completed, you will receive the message "Your database was rebuilt successfully."
5. Click Done.
   
   For More information visit: http://support.microsoft.com/kb/2360509

You can also restore you outlook 2011 for mac emails via this application: Outlook Mac Database Recovery Tool