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Send a real, printed letter with one API call. Give Dairo a PDF and a postal address; Dairo prints it, encloses it, posts it, and tracks it to the mailbox. Fairo is the physical-mail side of Dairo — the same API and keys you already use for email, pointed at the postal network.
Letters use two scopes: letters:read for listing, fetching, delivery events, and price quotes; letters:send for creating and canceling letters, and for creating batches and templates.

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How it works

1

Provide the document

Pass the PDF inline as pdfBase64, reference a file already in Dairo with file (an email attachment or a storage object), or render a stored letter template by templateId. Exactly one source per letter, plus a fileName for your records. Bringing your own PDF? Check it against the layout contract with POST /v1/letters/verify first — GET /v1/letters/requirements returns the machine-readable spec plus compliant starter templates.
2

Address it

Set the recipient in to, with an optional from sender block. country (ISO 3166-1 alpha-2) is required, and the address needs a street or a poBox.
3

Pick print and delivery

Color or grayscale, one side or two, and a delivery class from economy to premium. Every option has a default, so a minimal request works.
4

Send it

autoSend: true (the default) queues the letter for printing and posting. autoSend: false stores it as a draft instead — nothing is printed, and you can still cancel it.
5

Track it to the mailbox

Dairo follows the letter for you. Read its status and event timeline back by id, subscribe to letter.status_changed webhook events, or have Dairo email you at each delivery milestone.

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A letter is one call

cURL
You get back a letter object with an id and status: "queued". From there the letter moves through the lifecycle — printed, posted, in transit, delivered — and Dairo keeps its status and delivery events current.
Physical mail is irreversible once it is in the postal network. You can cancel a letter while its status is draft, queued, processing, printable, or submitted — never once it is in_transit. Quote first with POST /v1/letters/price and pass an idempotency key on create so a retry can never print the same letter twice.

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Options at a glance

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Go deeper

Send a letter

Create, list, get, cancel, and price — the full API walkthrough in cURL, TypeScript, Python, and the CLI.

Print & delivery options

Color vs. grayscale, simplex vs. duplex, delivery classes, and payment slips.

Status & tracking

The status lifecycle, the event timeline, webhook events, and owner email notifications.

Letter templates

Design the branded letter once, leave the address window blank, and send by id.

Send a batch

One template, up to 1,000 recipients, in a single call.

Pricing

Get the exact cost of a letter before you send it.