actually its not mail fraud... but your utility can refuse them.. so your bill won't be paid.. Con(solidated) Ed(ison) of NY does refuse all postage due mail, no matter what the return address (but you can pay for no fee over the phone.. and if you call from work...)

here in the US they are inclined to throw you out of the hosptial the minute you wake up from recovery, so if you send a get well to the hosptial, & you want the person to get it...put on a stamp, and their home address as a return. then the post office will in effect forward it for you.

(when toll road were cheaper, we sometimes would pay the toll for the car behind us.. (total strangers..) and tell the toll collector a story.. then the driver behind us, would try to track us down.. great fun.)