Which term describes packages that cannot be delivered and are sent back?

The term that describes packages that cannot be delivered and are sent back is "Return to Sender." This phrase is commonly used in mailing and shipping contexts to indicate that an item cannot be delivered to the intended recipient for reasons such as an incorrect address, the recipient refusing the package, or the recipient no longer residing at that location. When a package is marked as "Return to Sender," it is typically sent back to the original sender for further action or clarification.

The use of this term is widely recognized in postal services and is an important part of the protocols for handling undeliverable mail, ensuring that it is properly processed and returned to the sender instead of being lost or abandoned.

In contrast, the other terms do not accurately capture the process of returning undeliverable packages. "Not Deliverable" may describe the status of a package, but it does not convey the action taken afterward. "Lost Mail" refers to packages that cannot be found and are unlocatable, while "Shipping Error" implies a mistake in the shipment, which may or may not lead to a return. Therefore, "Return to Sender" is the most precise term for packages that are undeliverable and subsequently sent back.