LetterAgent
Mail physical letters by just asking your AI assistant.
Home > Guides > USPS vs UPS vs FedEx
For letters and documents, use the postal service: USPS in the United States, Canada Post in Canada. It's cheaper than a courier for anything that fits in an envelope, and only the postal service can deliver to a mailbox or a PO box. Reach for UPS or FedEx when you need overnight speed, a heavy document package, or detailed tracking.
| Situation | Best choice | Why |
|---|---|---|
| A letter or a few pages | USPS / Canada Post | Cheapest option by far; couriers charge parcel rates for what is still a letter |
| Documents to a PO box | USPS / Canada Post | Couriers generally can't deliver to PO boxes at all |
| Need it there tomorrow morning | UPS or FedEx overnight | Couriers' overnight networks are built exactly for this |
| A thick binder or box of files | UPS or FedEx | Better handling and tracking for heavy items than a padded mailer |
| Proof the recipient got it | USPS Certified / Canada Registered | Signature-style proof of delivery at a letter's price |
| International documents, fast | UPS or FedEx | Faster customs handling and end-to-end tracking than postal |
Two legal facts give the postal service a monopoly on your mailbox. In the US, only USPS may place items in a mailbox: it's a federal offense for anyone else, including UPS and FedEx drivers, to do it. That means a courier delivering "a letter" will leave it at the door or hand it over, never in the box. And PO boxes belong to the postal service, so UPS and FedEx generally can't deliver into one. If your recipient's address is a PO box, the courier option is off the table before you start.
Then there's price. Couriers price everything as a parcel; a three-page letter sent UPS overnight can cost many times what a stamped envelope costs. For documents where speed doesn't matter, the postal service's letter rates are the whole reason envelopes still exist as a format. In Canada the same logic holds with Canada Post: lettermail for letters, courier for everything urgent or heavy.
Speed is the obvious one. If a signed contract must be in someone's hands by 10:30 tomorrow morning, USPS Priority Mail Express exists, but the courier overnight networks run more flights, more often, and their on-time guarantees for overnight documents are the industry standard. The second win is tracking granularity: courier tracking shows a package moving through facilities in near real time, while postal tracking updates are coarser.
The third win is weight. Once your "documents" become a thick stack, a binder, or a small box of files, courier ground or express service handles it better: sturdier packaging options, automatic insurance up to a decent value, and no ambiguity about whether it counts as a letter or a parcel. A good rule of thumb: if it fits comfortably in a standard envelope, mail it; if you need a box or a padded mailer, compare the courier's quote before defaulting to the post office.
Couriers include detailed tracking and delivery confirmation by default, which is part of what you're paying for. But the postal service isn't far behind for documents: USPS Certified Mail (or Canada Post Registered Mail) adds tracking plus a record of delivery, at a fraction of courier prices. For legal or contractual documents where you need to prove the other party received them, certified or registered mail is usually the sweet spot: real proof, letter-sized price. Couriers earn their premium when the proof needs to arrive tomorrow.
Ready to mail it? Send your letter with LetterAgent: describe it to your AI assistant, approve the exact quoted price, and it's 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