When you send a message and a something goes wrong, gourmet.spamgourmet.com's Mailer-Daemon writes you back about it.
But if the address has 0 remaining messages, you'll never wrong your message wasn't sent!
I suggest having gourmet.spamgourmet.com's Mailer-Daemon as a built-in exclusive sender. Perhaps have an opt-in/out choice for it so no one will complain. You might add a check to make sure it's the real Mailer-Daemon.
What do you think?