Put a few upside down and backwards. When an extractor receives cash, no matter how small an amount, he has to take it to a special desk and fill out of few nasty forms. Like on the back of a Kroger sack. Any foreign fasteners or the like have to be removed and put away. Any signature has to verified and then date stamped.
Big envelopes have to be torn and sorted differently than regular business size ones.
An added bonus to the big envelope is that they take priority over other mail, so the workers can hurry up and deal with your mess. These are just a few of the fun and exciting things you can do with the man. These methods are only recommended when you owe money.