5.0 Returning Mail 5.1 Nonmailable Nonmailable matter is returned to the sender immediately. 5.2 Refused Mail Returnable mail is returned if refused by the addressee. Mail of all other classes is returned to the sender if appropriately endorsed to guarantee return postage. Other returnable mail is treated as appropriate for the class of mail and the sender's instructions except as noted below. The receipt stays attached to the piece and is returned to the sender.
Registered mail is returned through the registry system.
The sender must sign a delivery receipt for returned Express Mail and for certified, COD, numbered insured, registered, and return receipt for merchandise mail. For 5 days if for delivery by rural or highway contract route carrier. For 10 days if for general delivery at an office with city carrier service. If the addressee notifies the postmaster of a delay in claiming the mail, the postmaster may hold such mail up to 30 days. For 15 days if for general delivery at an office without city carrier service.