United State Postal Service (USPS) is the world’s best core service provider to its customers. USPS when deliver to final destination and if by chance or some problem not found the recipient available then post carrier bring back the package to the post office and try the next day in business hours and still not found anyone then he doesn’t give the third try it will be put into Dead Letter Box.
After putting the package in the dead letter box and anyone come and ask for the package then it will be handed over to that person.
If long time passed on and no one came to claim that or receive that then it will be destroyed as with passage of time.
But as we have look, then there is no need for the return address but this proves to be wrong because if packages remain undelivered because of some reasons then how will USPS will return the package to the sender.