Registered mail is a postal service in many countries which allows the sender proof of mailing via a receipt and, upon request, electronic verification that an article was delivered or that a delivery attempt was made. Depending on the country, additional services may also be available, such as:a chain of custody, where the posted item has its details recorded in a register to enable its location to be tracked, sometimes with added insurance to cover loss; a return receipt, called an avis de réception, which provides a postcard or electronic notification with the date of delivery and recipient signature; restricted delivery, which confirms that only a specific person or authorized agent will receive the mail, and; certified mail, in the United States.

A postage stamp is a small piece of paper issued by a post office, postal administration, or other authorized vendors to customers who pay postage. Then the stamp is affixed to the face or address-side of any item of mail—an envelope or other postal cover —which they wish to send. The item is then processed by the postal system, where a postmark or cancellation mark—in modern usage indicating date and point of origin of mailing—is applied to the stamp and its left and right sides to prevent its reuse. Next the item is delivered to its addressee.