(a)Official letters, book packets and parcels on which postage has not been prepaid or sufficiently paid shall, if duly superscribed "On His Majesty's Service" or "On Service" and inscribed by the sender, be received by the addressee who shall pay the charges due.(b)Letters and other postal packets sent by private individuals or associations without prepayment of postage on with postage insufficiently paid shall ordinarily be returned unopened to the post office of delivery.
