Post office boxes are a major location for receiving mail in the United States. For some people in certain rural areas, P.O. boxes are the only option for receiving mail. For others, they are a convenient choice, perhaps because their business is located near a post office. But receiving your mail in a post office box comes with certain disadvantages, because not all mail can be delivered to a post office box.
Anything sent via UPS cannot be delivered to a post office box. UPS requires a physical address. According to the UPS website, "We do not deliver to P.O. Boxes. If a shipper should use a P.O. Box address, the recipient´s telephone number must be included on the label." The phone number allows the UPS driver to telephone the recipient and arrange for a home delivery.
Many packages are just too large to fit in a post office box. In most cases, as long as the package was sent to the P.O. box address via the US Postal Service, the package will remain on the premises of that post office for the recipient to pick up in person. Generally, a slip will be placed in the recipient's box indicating that the package is being held. In some cases, the sender of a particular technological product, like an i-Pad or i-Phone, will not deliver their products to a P.O. box address.
With certain legal documents and other certified mail requiring the recipient's signature, the local post office will, as with large packages, place a slip in the post office box asking the recipient to sign the proper forms at the desk during regular business hours.
According to the US Postal Service website, while "all" mail classes and types can be sent to a box, the recipient has a limited window -- a required number of business days -- in which to pick up the package or the package will go back to its sender. This creates problems when you are away on vacation. As the U.S. Postal Service website states, "If the item requires a signature, a notice will be left. If the second attempt is unsuccessful, the item will be returned to the sender after the required number of business days have elapsed."