No longer at this address.

Is Mac mail is remembering email addresses you haven't used in weeks, months, years (you start to type an address in the To: field, and outdated versions of your contact's email address pops up)? Here's how to get rid of them.

On the menu bar, click Window>Previous Recipients.

Then you can sort them by Name, Email Address, or Last Used. If you select Last Used, you can get rid of the ones you have not used in a year by selecting one, then holding the SHIFT key, and selecting the last one in the pile you want to remove, then click Remove From List.