Admin configurable footer field for notification emails

I've noticed that users who subscribe to the notification module on one of my sites often don't take the time to figure out how to unsubscribe later on; they simply change their email to blank in edit my account. Then I have to go track down in the db the user with the blank email that also has notify.module enabled.

And it's not that they are not trying. I tracked a user one time who had just removed their email from their account, and they looked around the site. They also visited the subscription module, obviously assuming that this was the service they had enabled so many months before. They simply gave up after a couple minutes of looking.

Admittedly, it would be good if notify.module would ignore sending out emails to users with no email listed, but another feature that would also help would be if the footer added at the bottom of the notify emails was configurable in the notify configuration section of admin. Would be easy then to create a more detailed footer message with better instructions on how to unsubscribe. It would also be more dersirable because it would be better if users did not remove their email address for other reasons.