LetterAgent
Mail physical letters by just asking your AI assistant.
Don't guess the ZIP code. Type the full street address into the free USPS ZIP Code lookup tool and it returns the correct ZIP code, including the four extra digits. A wrong ZIP code sends your letter to manual sorting or, worse, to the wrong sorting facility. In Canada, the Canada Post postal code finder works the same way.
| Situation | What to do |
|---|---|
| You know the street address but not the ZIP | Use the USPS ZIP Code lookup (or Canada Post postal code finder); enter the full address, not just the city |
| You only know the city and street name | The lookup can list every ZIP used on that street; pick the range that matches the address |
| The recipient moved recently | Look up the new address fresh; old ZIP codes linger in search results and saved contacts |
| You truly cannot find it | The letter may still be delivered from the street address, but expect delays while clerks work it out |
The postal sorting system reads the ZIP code first and routes the envelope based on it. If the ZIP you wrote points to a different city than the street address, the machine sorts it to the wrong processing plant. Somebody there has to notice the mismatch, read the address by hand, and re-route it. That is days of delay, and it is entirely avoidable.
A wrong ZIP code is also one of the most common reasons a letter never arrives at all. ZIP codes get reused across states, so a guess that looks plausible can quietly drop your letter into the wrong metro area. The street address does not save it if nobody looks past the ZIP line.
Go to the USPS ZIP Code by Address page and enter the street address, city, and state. It returns the standard ZIP+4: five digits, a hyphen, and four extra digits that narrow delivery to a specific block or building. Use all nine digits. The extra four cost you nothing and help the sorter place the letter in the right carrier route.
The tool also fixes mistakes you might not catch. If you type the street with a wrong suffix (Ave instead of Blvd) or an outdated city name, it returns the corrected, standardized address. That matters because the lookup result is the version of the address that USPS's own equipment recognizes.
Canadian postal codes are six characters: letter, digit, letter, digit, letter, digit, with a space in the middle. Canada Post's postal code finder works like the USPS tool. Enter the street address and municipality, and it returns the correct code plus the standardized street spelling.
Canadian postal codes are more granular than US ZIP codes. A single US ZIP code can cover tens of thousands of addresses; a Canadian postal code often covers a single side of one city block. That makes a wrong postal code in Canada even more likely to misroute a letter, so the lookup step is not optional there either.
Sometimes, yes. A complete, accurate street address with a clear city and state gives clerks enough to work with, and a clerk may look the ZIP up for you. But it adds a manual step at every handling point, and automation skips the envelope entirely. Think of a missing ZIP as trading two minutes of lookup for several days of possible delay.
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