MailMate Bundle to unsubscribe from mailing lists that expose a List-Unsubscribe header
Invoke from keyboard shortcut ^U or menu Command → ListUnsub → List Unsubscribe.
First looks for a mailto: URI in the List-Unsubscribe header. If found will automatically send an unsubscribe email to that address.
Next looks for a http URI in the List-Unsubscribe header. If found will open that URI in the default web browser.