Written by: Timur Lesov

August 14, 2025

Updated on August 12, 2025

Shipping packages to a United States Postal Service (USPS) PO Box-or any similar post office box service-can raise many questions. Below is a thorough exploration of the topic, covering eligibility, carrier policies, packaging tips, tracking considerations, alternatives, and best practices. Whether you need to send gifts, business shipments, personal items, or returns, this guide will help you understand “can I ship a package to a PO Box?” from every angle.

1. Understanding What a PO Box Is

A PO Box (Post Office Box) is a secure, numbered box located inside a post office facility. Customers rent these boxes from USPS or, in some countries, from national postal services. PO Boxes serve individuals and businesses who need:

Key characteristics:

• A stable mailing address separate from a physical residence
• Privacy and security for personal or small-business mail
• Reliable delivery in areas with unreliable home delivery
• A convenient address for frequent travelers

Understanding these basics helps clarify what can and cannot fit into a PO Box and informs proper carrier selection.

• Size Limitations: PO Boxes come in various sizes (e.g., “5” is small; “7” is large). They accommodate letters and small parcels, but very large boxes may not fit inside.
• Access Hours: Customers can visit the post office lobby or, in some locations, retrieve mail via curbside by showing a key or combination.
• Mail Forwarding: Some USPS locations offer mail-forwarding services for when customers relocate.

2. USPS Policy: Shipping to a PO Box

2.1 Eligible Services

USPS is the only carrier that can deliver to a PO Box directly. These are the most commonly used USPS services for PO Boxes:

All of the above can be addressed to “PO Box [number], [City], [State] [ZIP].” Flat-rate packaging for Priority Mail fits within size constraints of most PO Boxes.

• First-Class Mail (envelopes, small packages under 13 oz)
• Priority Mail (flat-rate envelopes and small boxes; weight up to 70 lbs)
• Priority Mail Express (overnight and 2-day guaranteed)
• USPS Retail Ground (formerly Standard Post; packages up to 70 lbs)
• Media Mail (books, educational materials up to 70 lbs)

2.2 Restrictions and Size Limitations

• Facility Constraints: If a package is too large to fit inside the assigned box, USPS will place it in an “outparcel locker” or “parcel pickup” area. The customer receives a notification slip in their box to retrieve it from the counter or parcel locker.
• Prohibited Items: Standard USPS prohibited items (hazardous materials, perishables without prior arrangement, etc.) apply equally to PO Box deliveries.
• Oversized Mail: Oversized or irregular packages that cannot fit inside a PO Box or parcel locker will be held at the Customer Service desk. Customers must present ID and pickup notice.

3. Other Carriers: UPS, FedEx, DHL and PO Boxes

Unlike USPS, private carriers such as UPS, FedEx, and DHL have more restrictive policies:

Key takeaway: If mailing to a PO Box, USPS is the only reliable choice. Private carriers will reject or reroute such shipments to a local post office, causing delays and complications.

• UPS: UPS won’t deliver to a PO Box. Shipments must go to a physical street address. UPS Retail Services now offer a “UPS Access Point” or “Deliver to Post Office” option (for simplified retail return or pick-up), but these are not direct PO Box deliveries.
• FedEx: FedEx requires street addresses. FedEx SmartPost (now FedEx Ground Economy) used USPS for “last-mile” delivery and could deliver to PO Boxes, but this service was retired in 2020.
• DHL: DHL Express and DHL eCommerce require a physical delivery address; PO Boxes are not accepted.

4. Address Formatting and Label Requirements

Ensuring accurate addressing is critical. For USPS, the proper format is:

[Recipient Name] PO BOX [box number] [City], [State] [ZIP+4] 

For private parcel lockers or third-party mailboxes (e.g., UPS Store, Mail Boxes Etc.), use “PMB” (Private Mail Box) instead of “PO BOX.”

• Box Number: Must include “PO BOX” in capital letters or “PMB” for Private Mailbox hires at third-party postal providers.
• ZIP+4: Whenever possible, include the 4-digit extension to expedite delivery. Example: 12345-6789.
• Return Address: Always add a valid return address to ensure return to sender if undeliverable.

5. Packaging Best Practices

5.1 Selecting Packaging

• Size and Weight: Verify your box or envelope dimensions against PO Box size. Flat-rate envelopes (e.g., Priority Mail Flat Rate Envelope) are ideal since they conform to standard dimensions.
• Durability: Use corrugated cardboard, padded envelopes, or bubble-lined mailers to protect contents.
• Waterproofing: For items prone to moisture damage, add plastic packaging or tape all seams.

5.2 Label Placement

• Visibility: Place the shipping label on the largest flat surface.
• Secure Attachment: Use clear packing tape to cover the entire label without obscuring barcodes or addresses.

5.3 Special Handling

• Fragile Items: Indicate “FRAGILE” on the exterior, but note such labeling doesn’t guarantee extra USPS care.
• Perishables: Avoid shipping perishable foods or flowers to PO Boxes unless using Priority Mail Express with proper insulation and expedited timing.

6. Tracking, Notifications, and Confirmation

6.1 USPS Tracking

Most USPS services include tracking:

• First-Class Package: Tracking number for parcels.
• Priority Mail & Priority Mail Express: Detailed tracking, including scans at acceptance, transit, and delivery (or pick-up).
• Delivery Notification: PO Box customers get a key-inighbor slip when a box-too-large parcel arrives. This slip itself typically lacks tracking, but online tracking will note “Delivered to PO Box” or “Available for Pickup.”

6.2 USPS Informed Delivery

USPS offers Informed Delivery: An email with grayscale images of incoming mail pieces (letters, not parcels) and approximate arrival notifications. Parcel tracking remains separate.

7. Common FAQs and Troubleshooting

7.1 “Can I ship a package to a PO Box?”

Yes-if you use USPS. Private carriers cannot deliver directly to PO Boxes.

7.2 “My parcel was refused at the PO Box-why?”

Check USPS tracking for specific scan events.

• Too large to fit inside the box
• Undeliverable due to incorrect address or missing ZIP+4
• Restricted item or missing signature requirement

7.3 “How long will USPS hold my parcel?”

• PO Box Lockers: Typically up to 15 days for general PO Box holders.
• Customer Service Counter: Usually held up to 15 days, then returned to sender.

7.4 “Can I send packages internationally to a US PO Box?”

• Only USPS Global Express Guaranteed (GXG), Priority Mail Express International, and Priority Mail International support delivery to US PO Boxes. Other international carriers may not.

8. Alternatives When PO Box Delivery Fails

When USPS cannot route a package directly to a PO Box, consider:

1. General Delivery
   • Address to a specific post office with “General Delivery” instead of a PO Box number.
   • Suitable for customers without a fixed address or transient living situations.
2. Third-Party Mailbox Services
   • Services like UPS Store or Mail Boxes Etc. provide “Private Mail Boxes” with street addresses.
   • Accept deliveries from all carriers.
   • Some services include mail scanning, forwarding, and package receiving.
3. Amazon Locker & Carrier Pickup Points
   • Amazon Lockers and carrier-designated pickup points allow secure self-service retrieval.
   • Not a traditional mailbox, but an option for shopping and returns.
4. Home/Business Street Address
   • Use a physical address for all carriers. Consider secure delivery locations like workplaces, neighbors, or parcel lockers at apartment complexes.

9. Shipping Tips for Businesses

Businesses shipping to customers who use PO Boxes should:

• Offer Multiple Shipping Options: Clearly delineate USPS versus non-USPS shipping. At checkout, disable UPS/FedEx for customers entering a PO Box.
• Display Box-too-Large Warning: Notify customers that large items may require pickup at the post office.
• Provide Accurate Weight & Dimensions: Avoid overcharges and ensure proper postage.
• Use USPS APIs for Real-Time Rates: Integrate postal rate calculators to reflect accurate USPS rates.
• Automated Address Verification: Validate PO Box ZIP+4 using USPS Address Matching Service to reduce errors.

10. Summary of Key Points

In essence, USPS is the exclusive carrier permitted to deliver to PO Boxes in the United States. All USPS domestic services-First-Class Package, Priority Mail, Priority Mail Express, Media Mail, and USPS Retail Ground-can be addressed to a PO Box. Private carriers (UPS, FedEx, DHL) require street addresses and do not deliver directly to PO Boxes. Oversized packages that exceed the physical confines of the box are held in parcel lockers or at the customer service counter, with notifications delivered to the box.

For seamless PO Box shipping:

By following these guidelines, individuals and businesses can confidently ship letters and packages to PO Boxes with minimal disruption and maximum reliability.

• Verify USPS service eligibility.
• Format addresses correctly (including ZIP+4).
• Use USPS flat-rate or size-appropriate packaging.
• Include return addresses.
• Track shipments via USPS online tracking.
• Offer alternative pickup methods when necessary.

Timur Lesov

Eco-freak, nerd, and green technology fanatic. I’m in favor of making eco-friendly living simple as well. I graduated from Berkeley in 2017. Studied environmental science and all things sustainability related. I create content and share simple tips for greening your everyday life. I think even small changes can make a huge difference and we can build a cleaner and more sustainable future.