Packages
If a parcel does not fit in a PO box, the postmaster will leave a note advising that customer to pick up that parcel from the counter. In some post offices, a key will be left in the PO box that corresponds to a larger, locked box (parcel locker) where the patron may pick up his or her package if a signature is not required. (Most often, in this case, once the key is used to open the larger, locked box, the key cannot be removed again by the patron, but the door cannot be secured either.) Notes will also be left in the PO box in respect of Cash on delivery (COD) and registered mail that has to be signed for.
In 2011, the United States Postal Service began a pilot program called "gopost" which installed larger boxes to handle package pickup from an unstaffed station. A given box can be used by multiple customers thanks to the integration of a computer which accepts a delivery code. The system uses U.S. Patent 6,690,997, issued Feb 10, 2004 to Michael A. Rivalto. Deutsche Post started a similar concept called a Packstation in 2001.
Read more about this topic: Post-office Box