In Outlook 2011, the database is fragile and often breaks at the slightest provocation. A bum database most often results in a non-launching Outlook: you'll click the Outlook icon, it'll bounce once or twice and then quit without any further information. Thankfully the fix is typically fairly easy.

  1. Press and hold the command and option keys on your keyboard and launch Outlook. The Outlook Database Utility will launch.
  2. Make sure your primary database (i.e. the one with the most recent modification date) is selected and click the "Rebuild" button. See screenshot 1. Depending on the size of your database, this may typically take between 5 and 30 minutes
  3. Once completed, you should see a message that the rebuild as successful. Click the Done button. See screenshot 2.
  4. Launch Outlook normally and you should be back in business!