LetterAgent
Mail physical letters by just asking your AI assistant.
Home > Guides > Texting a fax number
No, you cannot text a fax number directly: SMS and fax are completely different systems, and a text sent to a fax line goes nowhere. If you need to get a message to a fax machine from your phone, use a text-to-fax app or an online fax service, which converts your message into a real fax transmission.
Your messaging app sees ten digits and assumes it is a phone, but the number on the other end is answered by a fax machine or a fax service with no SMS inbox. The text is delivered to a device that has no idea what to do with it, so it sits unread or is discarded. Some carriers return a delivery failure; most just show "delivered" while nothing meaningful happened. "Delivered" in your messaging app means it reached the carrier's system, not that a human or a fax machine read it.
It bridges the two systems. You type your message, or attach a photo of a document, in the app, and the app's servers convert it into a fax transmission and dial the fax number for you. The recipient's machine receives a perfectly ordinary fax; it has no idea the message started life as a text on your phone. This is the same trick behind faxing from email: the app translates between a modern interface and the old fax protocol.
| What you want | What actually works |
|---|---|
| Send a quick note to a fax number | A text-to-fax app that converts your message into a fax |
| Send a document photo from your phone | A fax app or online fax service that accepts uploads |
| Text back and forth with the recipient | Not possible: fax is one-way document delivery, not chat |
| Confirm the fax arrived | The app's delivery confirmation, not your messaging app's "delivered" tick |
Keep expectations modest. Formatting rarely survives: your carefully arranged text usually arrives as a plain page, so treat it as a note, not a designed document. Photos of documents work, but a blurry photo faxes as a blurry page, so check the image before you send. And there is no reply channel: if the recipient wants to respond, they fax or call you back on your real number. Always include your callback number in the message itself.
Two, and they pull in opposite directions. On one side, fax lines are point-to-point, which is part of why hospitals and law offices still use them. On the other, a text-to-fax app routes your message through the app provider's servers, so your document passes through a third party before it becomes a fax. If the contents are sensitive, check the app's privacy terms before sending, and prefer a service that states how it handles and deletes your documents.
That is close to how LetterAgent works. You describe the fax to your AI assistant instead of typing it into a fax app: per-fax quote with the page count verified, you approve the exact total, one-time Stripe payment, and the fax is sent to US and Canadian fax numbers. No inbound faxes: LetterAgent sends only. The service is currently in testing, so treat faxing as available in testing and confirm current status with your assistant before relying on it for anything urgent.
Ready to fax it? Fax with LetterAgent: describe it to your AI assistant, approve the exact quoted price, and it is sent.
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