OS X’s Mail application, like many others, keeps a list of recent email recipients. When typing in a recipient in a new message, Mail will try to help you along by autocompleting based on your first few keystrokes. I’ve mistyped email addresses before (okay, all the time) and if I got at least the first few characters right, then Mail may end up reusing my mistakes. A simple action in Mail will clear a learned address.
To remove an unwanted address from the recent recipient list, select it in the To, Cc, or Bcc field or an email composition and click on the little pull down arrow to the right of the address. This will reveal a menu of selections as show in this image:
Click on the Remove from Previous Recipients List option and you’re set.
