Box in a U.S. Postal Service facility, opened with a key or combination lock, that is used for the delivery of mail to an addressee who rents the box. A group of lockboxes that constitute a carrier route is called a lockbox section or Post Office Box Station. Bill payment envelopes are often addressed to lockboxes, which, as part of an arrangement with the recipient's bank, accelerate the processing of deposits, thus helping cash flow.




