TrekBBS: The source for all your Evil-Macgyver solutions to everyday life.get some plastic explosive, stick it to the bottom of the box, rig the door so the act of the mail carrier opening it primes the explosive and a second opening of the door (without first deactiviating the charge) detonates it, problem solved
ONly if he can do it with a paper clip as one of the items.
you can use a paperclip to poke a button on the primer