The Global Address List is automatically enabled on your account, but you can make sure with these steps:

  1. Open Airmail.
  2. Open Airmail Preferences (⌘,)
  3. Click on the settings icon next to the MS Exchange account.
  4. Click on the 'Composer' tab
  5. Make sure the "Global Address List" is ticked.
  6. Click on "Save".

Did this answer your question?