Suckerfish on the Side of Your Whale

So a customer sends an e-mail to a nonexistent address. Naturally, the mail server returns an undeliverable message. In this case, the particularly relevant part of the error message reads "MAILBOX NOT FOUND".

The customer replies (to the mailer-daemon, yes, in our company, I get these messages) saying "The mail shute [sic] is inside the front door. Please deliver."

At first I laughed, thinking a customer was being a bit amusing. Unfortunately, after looking up others' comments about this particular individual, I am fairly certain there was no joke here. Except for the cruel, sick joke that was the brief glint of faith I had in humanity.