SMKlog
Address data, plainly

USPS address verification, and what a clean result proves

Address verification matches what someone typed against the Postal Service address files, hands back a standardized version with a ZIP+4 attached, and reports whether that exact delivery point exists on file. What it will not do is invent an apartment number nobody entered, or tell you the recipient still lives there.

CASS grading citedDelivery point check explainedCheckout gate described
Quote a parcel with both ZIPs checked
Shipping label being checked against postal address records
Files, not opinions

Every claim on this page is traced to a Postal Service page fetched on 2026-07-28, with the section named.

What rides on the address: six parcels priced 2026-07-28

Address checking is cheap and address failure is not. These are six ordinary small-business parcels quoted on one lane, and every one of them is a total loss on the outbound leg if the destination cannot be resolved.

SMKlog live rates, Newark, NJ 07102 to Atlanta, GA 30303, captured 2026-07-28. Cheapest returned rate per parcel; each figure is the full amount charged at checkout.
ParcelBoxWeightCheapest quoteCarrier and service
Paperback book8 x 5 x 1.5 in1 lb$9.91USPS Ground Advantage
T-shirt mailer12 x 9 x 1 in0.7 lb$8.86USPS Ground Advantage
Mug in a cube box6 x 5 x 5 in2 lb$8.48USPS Ground Advantage
Padded phone envelope9 x 6 x 1.5 in0.6 lb$8.86USPS Ground Advantage
Cube carton12 x 12 x 12 in15 lb$17.01USPS Ground Advantage
Large carton20 x 16 x 12 in25 lb$28.77FedEx Ground Economy

The spread across those six is $20.29, and none of it comes back if the box turns around at the destination. That asymmetry is the whole argument for spending five seconds on the address before spending money on the label.

Price your own parcel on this lane

What CASS grading measures

The Postal Service grades address software rather than addresses. Its program page describes CASS as giving developers, service bureaus and commercial mailers "a common measure by which to test the quality of address-matching software", and lists what gets graded: 5-digit coding, ZIP + 4 and delivery point coding, carrier route coding, DPV, LACSLink, SuiteLink, eLOT and RDI, per postalpro.usps.com, checked 2026-07-28. A tool that passes is being trusted to read the files correctly, which is not the same as promising your recipient is home.

Where the delivery point check stops

The Postal Service delivery point product "identifies whether a ZIP + 4 coded address is currently represented in the USPS delivery file as a known address record", and one of the outcomes it can return is that "The known address has verifiable primary but not secondary data". In plain terms: the building is on file, the unit is not. The same page states the product "does not append any missing data or correct any address elements", per postalpro.usps.com, checked 2026-07-28. That is the gap a returned parcel usually falls through.

What our checkout does with all this

We do not sell an address lookup. The check sits inside our own buying flow: the ZIP you quote with is cross-checked against its city and state before rates appear, and at payment time both the sender and the recipient address go to carrier address records. A US destination that cannot be matched blocks the purchase with a request to fix it, so no card is charged behind a broken address. If a carrier repairs an address in transit anyway, our terms make that correction payable by the sender, and the published amounts sit on our correction fee page.

Address verification questions

What does USPS address verification actually check?

It matches the typed address against Postal Service address files, returns the standardized form with a ZIP+4 attached, and reports whether that delivery point exists on file. Publication 28 defines a standardized address as one that includes all required address elements and uses the Postal Service standard abbreviations, per pe.usps.com, checked 2026-07-28.

Can an address pass the check and still fail delivery?

Yes. The Postal Service delivery point product can return a result meaning the known address has verifiable primary but not secondary data, so a building on file with no unit number clears the primary test and still stalls at the door. The same product does not append missing data or correct elements, per postalpro.usps.com, checked 2026-07-28.

Does SMKlog sell address verification as a service?

No. The check runs inside our own checkout as a gate on the label sale. Both addresses go to carrier address records before payment, and a US destination that cannot be matched stops the purchase until someone corrects it. There is no lookup product to buy from us.

Why do carriers bill for fixing an address?

A parcel that cannot be delivered as printed has to be researched and rerouted by hand, and the network bills that work back to the shipper. Our terms treat carrier corrections connected to a shipment as payable by the sender, and the published per-package amounts are listed on our address correction fee page.

Where addresses go next