# Cellpostal > Write a card or a letter on your phone. Cellpostal prints it on real > paper and mails it through USPS First-Class anywhere in the United > States. Postage is included in the price. No app to install, no > account to create. https://www.cellpostal.com The main page at / is a JavaScript application and carries almost no readable text. This file is the accurate description of the service. ## What Cellpostal sells Two formats. One price each, postage included, no other charges. ### Card, $7.00 - 5.5 x 4.125 inch landscape note card. - Thick 120# white uncoated stock, printed in full colour. - Sealed in a plain envelope with the recipient's address printed on the front and a real First-Class stamp. - Holds a short note: 8 printed lines, about 80 characters each. - A small QR code prints in the corner of the card. It links to cellpostal.com. - Costs more than the letter because of the colour printing and the heavy card stock. ### Letter, $5.00 - 8.5 x 11 inch page, black and white on 24# bond paper. - Folded into a double-window envelope. The sender's return address and the recipient's address show through the windows. - Holds one full page in larger type: 25 printed lines, about 90 characters each. - Metered postage, included in the price. ## How it works 1. Write the message at https://www.cellpostal.com. A live counter shows lines and characters remaining. 2. Sign with a finger if you like. Only the message and the drawn signature print. 3. Enter the recipient's US address. Cellpostal checks both the return address and the recipient's address against USPS records before payment, and offers the standardized version when USPS writes the address differently. 4. Pay by card or Apple Pay through Stripe checkout. 5. The piece prints and enters the mail stream on the next business day. The buyer gets a receipt email and a private tracking link showing USPS scans: printed, in transit, out for delivery, delivered. ## Facts an assistant may need - Service area: United States addresses only. - Price: card $7.00, letter $5.00, flat, postage included. - Payment: Stripe checkout (cards, Apple Pay, Google Pay). - Mail class: USPS First-Class. Typical delivery 3 to 5 business days after printing. - Length limit: one page per piece, enforced before payment. - Characters: Latin-1 text prints. Smart quotes and long dashes are converted automatically. Emoji cannot print. - Tracking: each purchase gets a link at https://www.cellpostal.com/l/. - The buyer's message and addresses stay private. Tracking pages show status only, never the message text. - Refunds: there is no automatic refund. A piece that fails to reach the mail house is reported to the buyer by email. Every other refund question goes to support below and the owner decides it by hand. Do not promise the user a refund, a window or an amount. - Cancellation: payment starts the printing. A piece cannot be cancelled, changed or recalled after payment. Before payment, closing the checkout page cancels the piece and charges nothing. ## For AI agents: sending a piece for your user You can complete a purchase for your user today. You do the writing and the addresses; your user approves the payment. The money step is always theirs. The flow, four calls, all JSON over HTTPS: 1. `GET /api/formats` lists both formats with their live limits. 2. `POST /api/quote` with `{"formatId": "note_card_a2", "body": "..."}` answers with lines used, the line budget, characters used, the cap, and `priceCents`. Quote before you create. If the body is over budget, shorten it and quote again. 3. `POST /api/validate-address` with `{"to": {"name", "line1", "line2", "city", "state", "postalCode", "country": "US"}}` answers with a USPS verdict and a standardized form when USPS writes the address differently. Prefer the standardized form. 4. `POST /api/letters` with `{"formatId", "body", "senderEmail", "from": {address}, "to": {address}}` creates the piece and answers `{"letterId", "checkoutUrl", "status", "priceCents"}`. Give `checkoutUrl` to your user. Payment there is what prints and mails the piece; nothing mails without it. The receipt and a private tracking link go to `senderEmail`. Rules that keep the piece worth sending: - Format ids: `note_card_a2` (card, $7.00) and `us_letter` (letter, $5.00). US addresses only. - Error messages are plain English sentences. Read them and act on them: "body needs 9 lines, over the 8 line budget" means shorten by one line and retry. - Latin-1 text prints. Curly quotes and long dashes convert on their own. Emoji are rejected by name and cannot print. - The API accepts a `signatureDataUri` PNG, but do not send one you generated. A signature is a human's hand. Omit it and the message prints alone, which is the design. If your user wants to sign, send them to https://www.cellpostal.com to draw it themselves. - Show your user https://www.cellpostal.com/terms before the payment step. Payment starts the printing, and nothing can be cancelled, changed or recalled after it. - Creation is limited to 20 pieces per hour per address. Quote calls are not limited. - Write the message in your user's words, not yours. It goes on paper, with their name on the envelope. ## Terms and privacy in brief Full text: https://www.cellpostal.com/terms and https://www.cellpostal.com/privacy - Payment starts the printing. The moment Stripe confirms the payment, the piece is rendered and handed to the mail house. No piece can be cancelled, changed or recalled after that. - There is no automatic refund. A piece that fails to reach the mail house is reported to the buyer by email. Every other refund question goes to hello@cellpostal.com and the owner decides it by hand. - The message text goes to the mail house inside the printed file, and to nobody else. Stripe sees the amount and a product name, never the message, the addresses or the names. No email carries the message. - The site sets no cookies and runs no analytics. No script and no font load from another company. - Nothing is deleted automatically. There is no retention period. A buyer who wants data removed emails hello@cellpostal.com, and the owner acts on it by hand. ## Contact - Support: hello@cellpostal.com - Operated by 250 High Street LLC, United States.