A PO Box is a USPS-only address, so UPS, FedEx and DHL Express cannot leave a parcel in it. A residential mailbox is served by every carrier but only for items that physically fit. The rules each network publishes for both, read 2026-08-11, together with what the choice means for the person shipping.
| Carrier | To a PO Box | To a home mailbox |
|---|---|---|
| USPS | Yes for every mail class. Parcels that don't fit in the box get a notice slip and hold at the counter. | Yes when the item fits and does not require signature. Otherwise a slip is left. |
| UPS | No. UPS cannot deliver to a USPS PO Box. | Yes to the door or porch, not the mailbox itself. Federal law bars non-USPS traffic from a USPS mail receptacle. |
| FedEx | No, with one exception: FedEx SmartPost hands off to USPS at the last mile, and that reaches a PO Box. | Same as UPS. The parcel goes to the door, never inside the mailbox. |
| DHL Express and eCommerce | DHL eCommerce hands off to USPS and does reach a PO Box. DHL Express to a physical address only. | DHL Express to the door. |
The federal rule under 18 U.S.C. Section 1725 makes any non-USPS delivery to a mail receptacle a fineable offence, which is why couriers approach the door and leave the mailbox alone even when it would be convenient.
USPS rents PO Boxes in five sizes, from XS (roughly 3 x 5.5 in opening) to XL (roughly 12 x 22 in opening). Anything larger than the XL cavity is held for pickup at the counter, and a slip drops into the box. Payment for the box is annual or six-month, priced by ZIP.
The USPS Domestic Mail Manual limits mail placed in a residential curbside mailbox to items that fit fully inside without protruding, without deforming the door and without blocking other mail. Parcels above that are left at the door or slipped for pickup.
Signature Confirmation, Certified Mail, Registered Mail and Return Receipt items are never left in the mailbox or the PO Box regardless of size. They wait at the counter for photo ID.
The buyer's address decides which services can be sold at all. If the ship-to reads P.O. Box, a UPS Ground label is going nowhere, and a FedEx Ground label is going nowhere. The label needs to be USPS or a FedEx SmartPost / UPS Mail Innovations product that ends at USPS.
| Item | Service |
|---|---|
| Envelope up to 3.5 oz | USPS First-Class Mail or Ground Advantage |
| Padded envelope up to 15.99 oz | USPS Ground Advantage |
| Small box under 20 lb | USPS Ground Advantage or Priority Mail |
| Fast delivery | USPS Priority Mail Express, which reaches every PO Box that is open on weekend delivery hours |
| Very large or heavy item | USPS Ground Advantage, or ask the buyer for a street address instead - a PO Box has a physical size ceiling |
A PMB street address at a private mailbox rental (UPS Stores, retail postal service centres) reads like a home address but is not one, and it is not a PO Box either. UPS, FedEx and USPS all reach a PMB when the address includes the # or PMB line correctly, because the store accepts on behalf of the renter.
A PO Box is worth the annual fee for anybody who receives valuable mail and travels, because a locked PO Box is safer against theft than an unlocked curbside mailbox and does not depend on somebody being home to sign. It is a poor primary address for e-commerce buyers because every UPS or FedEx-labelled parcel gets refused. A street address for parcels plus a PO Box for financial mail is the most flexible pairing.
No. A PO Box is a USPS-only receptacle and non-USPS carriers cannot access it. Any UPS label to a P.O. Box address is undeliverable and comes back.
FedEx Ground and Express will not. FedEx SmartPost reaches a PO Box because the last leg is handed to USPS, but the sender has to select that service specifically.
No. Federal law bars non-USPS traffic from a mail receptacle. UPS, FedEx and DHL leave at the door, on the porch or with a neighbour when authorised.
Ship USPS. Ground Advantage covers most sizes, Priority Mail is faster, and Priority Mail Express is the fastest option that reaches every PO Box.
No. A PMB is a private mailbox at a store, addressed as a street address with a PMB or # line. It accepts UPS, FedEx and USPS because the store signs on your behalf.