City, rural, contract, box and counter. Which one serves an address decides who can deliver and what it costs.
Four destinations, one box, four different answers
The cleanest way to see deliverability in money is to hold the parcel constant. Below is the same 12 x 10 x 6 in box at 5 lb sent from Newark to four places of increasing difficulty, all quoted on the same day.
| Destination | Cheapest quote | Carrier and service | Quoted transit |
|---|---|---|---|
| Atlanta, GA 30303 | $13.52 | UPS Ground Saver | window not quoted |
| Bozeman, MT 59718 | $19.14 | UPS Ground Saver | window not quoted |
| Lusk, WY 82225 | $20.60 | UPS Ground | 6-7 business days |
| Ketchikan, AK 99901 | $22.89 | USPS Ground Advantage | 15-16 business days |
The full board on the hardest of the four
| Carrier | Service | Price | Quoted transit |
|---|---|---|---|
| USPS | Ground Advantage | $22.89 | 15-16 business days |
| UPS | Ground Saver | $32.54 | window not quoted |
| USPS | Priority Mail | $34.55 | 9-10 business days |
| FedEx | Ground Economy | $61.15 | 15-16 business days |
| USPS | Priority Mail Express | $107.72 | 12-13 business days |
Look at what dropped off that second board: no UPS Ground and no air tiers from UPS at all, and the FedEx economy row landing at nearly three times the postal one. That is deliverability expressing itself as a price rather than as an error message, and it is why a quote on the exact ZIP tells you more than any state-level guess.
The five route types, as the files code them
The Postal Service assigns every delivery a four-character carrier route identifier whose first character is a letter: B for a PO Box, H for a contract route, R for a rural route, C for city delivery and G for general delivery. A parallel record type code marks addresses as general delivery, high-rise, firm, street, PO Box or rural route and contract. Both come from the Address Information System Products Technical Guide on postalpro.usps.com, checked 2026-07-28, and together they answer the question of what kind of place you are shipping to.
Box-only ZIPs and segments with no delivery
Some ZIP codes have no street delivery in them at all. The same guide defines a ZIP classification code with values including P for a ZIP code having only Post Office boxes, U for a unique code assigned to a single organization, and M for a military code. Separately, add-on codes for non-delivery areas carry the letters ND in place of the segment digits, and the guide describes those as areas the Postal Service does not deliver to, such as vacant lots and land bordering railroad tracks. An address in either category will not accept a normal parcel however carefully it is written.
Three checks that cost nothing
Start with the Postal Service address lookup on usps.com, which tells you whether the street address resolves and what its code is. Then ask the recipient directly which of the five they have, because a household on a box-only ZIP already knows. Last, run the ZIP through a quote and read the board: a destination that only returns postal rows is telling you the private carriers cannot serve it. Our checkout adds a final gate, refusing payment on a US destination that carrier address records cannot match.
Deliverability questions
How do I find out whether USPS delivers to an address?
Run the street address through the Postal Service lookup on usps.com to see whether it resolves, and ask the recipient which kind of delivery they have. Postal files code every delivery as a PO Box, contract route, rural route, city delivery or general delivery, and that code is what decides who can bring a parcel.
What is a PO Box only ZIP code?
It is a ZIP with no street delivery behind it. The Postal Service address products guide carries a classification code with the value P for a ZIP code having only Post Office boxes, alongside U for a code assigned to a single organization and M for a military code, per postalpro.usps.com, checked 2026-07-28.
Why do UPS and FedEx not quote some addresses?
Because they cannot serve them, or cannot serve them at every tier. Our 2026-07-28 board to Ketchikan, Alaska returned three postal rows, one UPS ground row and one FedEx row, with no UPS Ground and no UPS air tiers offered at all on that lane.
Does a hard-to-reach address cost more?
Considerably. The same 12 x 10 x 6 in box at 5 lb quoted $13.52 to Atlanta, $19.14 to Bozeman, $20.60 to Lusk and $22.89 to Ketchikan on 2026-07-28, and the Alaska row carried a 15 to 16 business day estimate on top of that price.