LetterAgent
Mail physical letters by just asking your AI assistant.
Home > Guides > PO Box street addressing
Yes, if your post office offers Street Addressing. Instead of "PO Box 123," you write the post office's street address followed by your box number, and the post office accepts packages from any carrier: UPS, FedEx, Amazon, and DHL, not just USPS. Both address styles reach the same box.
| Address style | Example | Who can deliver to it |
|---|---|---|
| Traditional PO Box | PO Box 123, Springfield, IL 62701 | USPS only |
| Street Addressing | 456 Main St, #123, Springfield, IL 62701 | USPS, UPS, FedEx, Amazon, DHL |
| Street Addressing (unit form) | 456 Main St, Unit 123, Springfield, IL 62701 | Same: any carrier |
Private carriers have always refused to deliver to "PO Box" addresses, because their systems and drivers are built around street addresses. That left PO Box holders stuck when a store only shipped UPS or FedEx. Street Addressing closes the gap: you give the sender the post office's own street address, the carrier drops the parcel at the post office, and the clerks sort it into your box by the box number. It is free for box holders where the post office offers it, and you sign up when you rent the box or add it later through your post office.
Use the post office's street address, then your box number as a suite or unit number. The "#123" and "Unit 123" forms both work; "PO Box 123" tacked onto a street address confuses carrier systems, so don't combine the two styles. Keep the city, state, and ZIP the same as your box's. One detail that trips people up: some store checkouts reject the address because they can't match it to a residence. If that happens, try the alternate format ("Unit" instead of "#") before giving up, because the mismatch is usually the store's validator, not your address.
Not every PO Box qualifies. The feature is offered at many post offices, but not all, and parcels are accepted at the retail counter during the office's hours, so a parcel dropped off late sits until the next business day. Oversized parcels that don't fit the box are held at the counter with a pickup notice, the same as any large USPS delivery. And the box still works exactly like a PO Box for regular mail: senders can use either format interchangeably, and both land in the same box.
Canada Post doesn't offer a US-style street-addressing feature for PO Boxes, but it does offer FlexDelivery, which solves the same problem from the other direction: a free parcel-receiving address at a post office of your choice, tied to your Canada Post account. Online orders ship to your FlexDelivery address instead of your home, and you pick them up at the counter. It accepts parcels from Canada Post; couriers like UPS and FedEx can't deliver to it, since the address is a postal facility. If a store only ships by courier, a Canadian PO Box alone won't help, which is exactly the gap Street Addressing fills in the US.
Ready to mail it? Send your letter with LetterAgent: describe it to your AI assistant, approve the exact quoted price, and it is printed and mailed.
LetterAgent is a working name. Prices include print, postage, and our service fee. US prices in USD, Canadian prices in CAD (Canadian prices exclude applicable sales tax, added at checkout). Currently in private testing.
Need help? Ask your assistant: it can check a job's status any time. If it ever can't handle something: hello@getletteragent.com