If a package is undeliverable, the USPS returns it to the sender. The post office sends packages which are both undeliverable and not returnable to the sender to dead mail for further processing in order to return them to the sender or addressee. When the USPS declares a package as dead mail, they have the right to violate the secrecy of correspondence to find its origin or intended destination.
Postal employees try to match articles found loose in the mail with their original packaging in order to return or forward them. The post office discards items considered to have no value, including unsigned letters, newspapers and circulars. Once the post office declares mail as a dead parcel, it is sent it to a mail recovery center where employees open it to determine the address of the sender or intended recipient. If an address is found, the package is sent with postage due. If the person receiving the forwarded package refuses to pay the postage due, the parcels become the property of the USPS. Dead mail for which the post office cannot find the rightful owner also becomes property of the USPS. At this point, the post office has the right to dispose of undeliverable mail through auction or donation to certain institutions.