Written by: Timur Lesov

September 03, 2025

Updated on August 18, 2025

Main Takeaway: The United States Postal Service (USPS) is the only carrier that can deliver to PO Boxes. To ship successfully to a PO Box, select USPS services, address and package your item correctly, adhere to size and content restrictions, and follow best practices to ensure timely delivery.

1. Why Only USPS Delivers to PO Boxes

Most commercial carriers-including UPS, FedEx, and DHL-cannot deliver to PO Boxes because they require a street address for their tracking and delivery systems. The USPS owns and operates the network of Post Offices and PO Boxes and thus is uniquely authorized to place mail and packages into them. If you attempt to use a third-party carrier for a PO Box delivery, the item will be returned to sender or redirected to the street address associated with the recipient, if one is on file.

2. Choosing the Right USPS Service

When shipping to a PO Box, you have several USPS service options. Choose based on speed, size, weight, and value of the contents:

• USPS First-Class Mail Best for letters, flats, and small packages under 13 oz. Delivery typically in 1–5 business days. Affordable but without detailed tracking for weight below 13 oz.
• USPS Priority Mail Ideal for packages up to 70 lb or larger envelopes. Delivery in 1–3 business days. Includes tracking and up to $100 insurance with USPS Flat Rate options available.
• USPS Priority Mail Express Fastest USPS option for overnight to 2-day delivery. Includes tracking, insurance up to $100, and money-back guarantee.
• USPS Retail Ground (formerly Parcel Post) Economical for heavier items up to 70 lb when speed is less critical. Delivery in 2–8 business days with tracking.
• USPS Media Mail Restricted to media items (books, DVDs, CDs). Slower delivery (2–8 business days) with tracking, but cost-effective.

3. Addressing Guidelines for PO Box Shipments

Correct addressing is critical to avoid delays or returns. Follow these rules precisely:

Recipient Name A valid recipient name or business name must match the name on the PO Box account.

PO Box Number Use the format “PO Box [number]” or “Post Office Box [number]” on its own line. Do not abbreviate “Box” to “Bx.”

City, State, ZIP Code Include the official city (usually the name of the Post Office where the box is located), the two-letter state abbreviation, and the five-digit or ZIP+4 code.

Optional Street Address for Business Boxes If the Post Office provides a street address equivalent (for real-time tracking), you may include “#” followed by the box number without “PO Box.” Always verify with your local Post Office.

Example:

Jane Doe PO Box 1234 Springfield IL 62701-1234 

4. Packaging Requirements and Size Restrictions

Maximum Dimensions

• Packages must not exceed 108 inches in combined length plus girth (2× width + 2× height).
• Maximum weight is typically 70 lb.

Flat Rate Boxes and Envelopes

• Flat Rate packaging is available in various fixed sizes; one price regardless of weight or distance (up to 70 lb).
• Dimensions range from small envelopes (9½″ × 12½″) to large boxes (12⅛″ × 12⅛″ × 5½″).

Sealing and Durability

• Use sturdy corrugated boxes or rigid envelopes.
• Seal all seams with quality packing tape.
• Reinforce corners and edges to protect contents.

5. Prohibited and Restricted Items

USPS enforces restrictions on what can be mailed to any address, including PO Boxes:

Always consult the latest USPS Publication 52 (“Hazardous, Restricted, and Perishable Mail”) for full details.

• Hazardous Materials: Flammable liquids, fireworks, certain batteries, and corrosive chemicals are largely prohibited.
• Perishables: USPS does not guarantee freshness; refrigerants are prohibited.
• Live Animals: Only specific live animals (e.g., snails, day-old poultry) under strict guidelines.
• Controlled Substances: Illicit drugs and paraphernalia are strictly banned.
• Alcoholic Beverages: Generally prohibited except under special permit.
• Prescription Medications: May be mailed only under certain conditions.

6. Tracking and Insurance

Tracking

• First-Class Mail parcels and larger services include tracking that shows delivery to the PO Box.
• USPS.com and the USPS Mobile app provide real-time status.

Insurance and Value Coverage

• Priority Mail and Priority Mail Express include up to $100 insurance.
• Additional coverage can be purchased in increments up to $5,000 for most services.

7. Drop-Off and Pickup Options

To ship to a PO Box, you can choose among these methods:

• Retail Counter at Post Office Hand items to a postal clerk, pay postage, and receive a receipt.
• Self-Service Kiosks Available 24/7 for purchasing postage and dropping off prepaid packages.
• Collection Boxes For Priority Mail Express and Priority Mail, small prepaid packages may fit in collection slots.
• USPS Pickup Service Schedule free USPS pickup at your residence or business for packages already labeled with postage.

8. International Shipments to US PO Boxes

USPS delivers international mail to domestic PO Boxes. Key points:

Example:

• Customs Forms: Complete PS Form 2976 or 2976-A, attaching it to the package.
• Address Format: Include country name above the PO Box line.
• Delivery Times: Vary widely; Priority Mail International averages 6–10 days, First-Class International 1–3 weeks.

John Smith PO Box 4567 Anytown NY 10001-4567 UNITED STATES 

9. Common Pitfalls and Troubleshooting

Mistakes in addressing or service selection can result in returned or delayed mail. Watch for these errors:

If a package is returned, check the return barcode and contact your local Post Office to resolve address issues.

• Incorrect ZIP+4: Use the precise ZIP+4 for the PO Box to speed sorting.
• Omitting “PO”: Leaving out “PO” causes confusion with street addresses.
• Using Non-USPS Carriers: UPS or FedEx labels on a PO Box will be refused.
• Oversized Items: Large parcels that don’t fit in the box may be held at the Post Office for pickup.

10. Best Practices for Bulk or Business Mailing

Businesses sending many packages to PO Boxes should consider:

• USPS Commercial Rates: Apply for a business account and use online postage providers for discounts on bulk Priority Mail and First-Class packages.
• Every Door Direct Mail (EDDM): If delivering marketing mail to all PO Boxes in a ZIP code, EDDM can be cost-effective.
• Automation and Barcoding: Use Intelligent Mail barcodes for flats and letters to improve tracking and delivery speed.
• Mailing Software: Integrate with USPS APIs to validate addresses and print postage in bulk.

11. Alternatives When USPS Is Not an Option

If you need the features of another carrier (for example, residential delivery confirmation or specialized handling) and the recipient only has a PO Box, suggest:

• Providing a Street Address: Some Post Offices offer street-style addressing (e.g., “123 Main St #4567”) for PO Boxes; verify availability locally.
• General Delivery: For travelers without a fixed address, USPS General Delivery holds mail at a Post Office under the recipient’s name for up to 30 days.
• Private Mailbox Services: Companies like UPS Store or Mail Boxes Etc. provide a physical street address and mailbox number, allowing FedEx and UPS shipments.

12. Step-by-Step Process to Ship to a PO Box

Shipping to a PO Box requires selecting USPS services, following strict addressing formats, and adhering to size, weight, and content restrictions. By choosing the appropriate service, packaging carefully, and using accurate addressing, senders can ensure reliable and efficient delivery to PO Boxes nationwide.

1. Select USPS Service Choose between First-Class, Priority Mail, Priority Mail Express, Retail Ground, or Media Mail based on size, weight, budget, and delivery speed.
2. Prepare Packaging Use USPS-approved boxes or envelopes. Seal securely and reinforce vulnerable areas.
3. Address Correctly Write recipient name, “PO Box [number],” city/state, and ZIP+4. Verify accuracy with the USPS ZIP Code Lookup tool.
4. Weigh and Measure Determine postage by weight and dimensions. Flat Rate options eliminate weight-based pricing up to 70 lb.
5. Purchase Postage At a Post Office counter, self-service kiosk, or online via USPS.com, ensuring you select “PO Box” delivery.
6. Attach Labels and Forms Affix postage label and any required customs declarations for international shipments.
7. Drop Off or Schedule Pickup Hand over at a Post Office, deposit in an appropriate collection box, or request a free USPS pickup.
8. Track Delivery Monitor status via tracking number. Notify recipient when delivered or held for pickup at the Post Office.

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.