Even sullen silence (known as dumb insolnce in the army) in the body of the email fails to deceive the ListRobot.
You have to send <Unsubscribe> in the message line (as you correctly did) to the appropriate address (which, alas ...).
It's something like [log in to unmask], but I can't remember exactly.  Perhaps the listmanagers, or someone, could assist the reluctant lurker in her no doubt completely warranted efforts to leave our company?