Customer guide
Send a letter.
LettersByLetter prints the piece and puts it in the USPS stream. This is the person path — one recipient in the wizard. Lists go through the API or MCP.
What you need
Addresses
A US From and To. Name, street, city, state, and ZIP. Save either side to the address book from the send screen.
The piece
A short composed letter, or a print-ready PDF up to 25 MB. Uploads keep embedded fonts. Compose embeds Times, Helvetica, or Courier.
A way to pay
Workspace credits (card or USDC), or pay the piece when you send. New accounts start at zero credits.
The send
01
Sign in
Open the workspace with Google, email, X (when enabled), or the demo account. New accounts start at zero credits.
02
Write or upload
Compose a short letter in the wizard, or drop a print-ready PDF (max 25 MB). Uploaded PDFs keep embedded fonts; compose uses Times, Helvetica, or Courier.
03
Add addresses
Enter From and To. Save either side to the address book for the next send. Multi-recipient lists go through the REST API or MCP, not a CSV upload in the wizard.
04
Choose a mail class
Pick First-Class ($1.49 page 1, then $0.25 per extra page), Certified Mail ($12.99 base piece + $0.25 extra pages, optional $2.40 Electronic Return Receipt), or a 4×6 postcard ($1.99 flat).
05
Pay and authorize
Spend org credits, pay by card on Square, or settle USDC via x402. Review the piece, then authorize the send. LetterStream prints and enters USPS; staging keys never buy postage.
Pick a mail class
First-Class
Invoices, thank-yous, ordinary correspondence. $1.49 for page 1, then $0.25 each extra page.
Certified Mail
Proof of mailing. $12.99 base (first page included), $0.25 extra pages, optional $2.40 Electronic Return Receipt.
Postcard
4×6 color, both sides. Flat $1.99. Not for multi-page documents.
After it leaves
The job lands in your dashboard. Status moves from queued toward mailed. USPS tracking appears when LetterStream returns it — not every First-Class piece will have a number.
Physical mailing is live on this deployment. Staging API keys (lbl_test_) are a developer sandbox and never purchase postage. A local checkout without LetterStream credentials stays in labeled demo and will not invent a successful live send.