Packages that, within a specified time frame, have not been picked up, accepted, or identified by the intended receiver are considered unclaimed. Unaccounted-for recipients, lost addresses, or unpaid customs fees may prevent these items from being delivered. Commonly held in transitory storage by courier services, postal services, or retail establishments, they may eventually be returned to the sender, auctioned off, or disposed of in compliance with policy. Large amounts of unclaimed shipments are occasionally put up for sale, luring buyers with the promise of a mystery package.

Unclaimed packages are those that, during a given time period, have not been picked up, accepted, or identified by the intended recipient. These packages might not be able to be delivered because of misplaced addresses, unaccounted-for recipients, or unpaid customs charges. Frequently kept in temporary storage by courier services, postal services, or shops, they may ultimately be given back to the sender, put up for auction, or disposed of in accordance with corporate policy. Sometimes unclaimed shipments are offered for sale in large quantities, giving customers the allure of a mystery box.