Yes, the post office has rules for managing the mail of the deceased. If you need to forward a single piece of mail, then you can cross out the address and write "Forward to" along with the new address on the envelope. If you wish to forward all of the deceased person's mail to a new address, you can complete a change of address form. The post office will need to verify that you are the executor or administrator of the estate before processing the change of address form.