How do I delete a previous recipient's email address from Mail?

Solution 1:

1. Fire up a "New Message" from the File menu (or use command + N)
2. Begin typing the address
3. When Mail starts to complete the address you want, hit the Return key to tell Mail to go ahead and auto-complete the address
4. Hover the mouse pointer over the address; a blue arrow will show up on the right hand side.
5. Click on the arrow, which brings up a drop-down menu. The menu contains several options, one of which is "Remove address." Click it, and it will remove the address from auto-complete.

Solution 2:

Under Mail's "Window" menu select "Previous Recipients" and you can delete any address you don't want.

Solution 3:

When the suggestion appears, just use the navigation to reach it then press delete on it, that's it.