> ## Documentation Index
> Fetch the complete documentation index at: https://docs.dairo.app/llms.txt
> Use this file to discover all available pages before exploring further.

# Welcome to Dairo

> One API for email, Telegram, Slack, agent-to-agent messages, and printed letters — sent from your own domain, with replies as structured threads.

Dairo is a messaging API. One send call delivers email, Telegram, Slack,
and agent-to-agent messages from addresses on your own domain — and can even
post a printed letter. Replies come back as structured threads you can read,
answer, or hand to an agent.

You verify a domain once, then send with a single call. Dairo authenticates
your mail, handles retries, bounces, and complaints, threads the replies, and
records every delivery event.

<CardGroup cols={2}>
  <Card title="Send email" img="https://mintcdn.com/dairo/pK0TZ5ICM74nt9cd/images/send-email.webp?fit=max&auto=format&n=pK0TZ5ICM74nt9cd&q=85&s=6b1ff1f61ac6c8e3cb939f11e7102383" href="/sending/sending-email" width="1000" height="667" data-path="images/send-email.webp">
    Transactional and marketing email from your own verified domains, with
    authenticated delivery and full tracking.
  </Card>

  <Card title="Send physical mail" img="https://mintcdn.com/dairo/pK0TZ5ICM74nt9cd/images/send-physical-mail.webp?fit=max&auto=format&n=pK0TZ5ICM74nt9cd&q=85&s=997125b682d38cf42f21aee0529a673e" href="/letters/overview" width="1000" height="667" data-path="images/send-physical-mail.webp">
    Turn a PDF into a real, printed letter that arrives in a physical mailbox —
    the same API, pointed at the postal network.
  </Card>
</CardGroup>

## What you can build

<CardGroup cols={2}>
  <Card title="Transactional email" img="https://mintcdn.com/dairo/pK0TZ5ICM74nt9cd/images/transactional-email.webp?fit=max&auto=format&n=pK0TZ5ICM74nt9cd&q=85&s=42c630d3cd9283a6982002bf14b8348d" width="1000" height="667" data-path="images/transactional-email.webp">
    Receipts, password resets, and notifications from your verified domain, with
    authenticated delivery.
  </Card>

  <Card title="Marketing & broadcasts" img="https://mintcdn.com/dairo/pK0TZ5ICM74nt9cd/images/marketing-broadcasts.webp?fit=max&auto=format&n=pK0TZ5ICM74nt9cd&q=85&s=f3265a49d3fdf5037d546df7808294e0" width="1000" height="667" data-path="images/marketing-broadcasts.webp">
    Group recipients into an audience and send to everyone in it. Members who
    opted out are skipped automatically.
  </Card>

  <Card title="Smart inboxes" img="https://mintcdn.com/dairo/pK0TZ5ICM74nt9cd/images/smart-inboxes.webp?fit=max&auto=format&n=pK0TZ5ICM74nt9cd&q=85&s=c2e290c357f12f5b5bdb2cd6c69191f4" width="1000" height="667" data-path="images/smart-inboxes.webp">
    Real addresses on your domain that receive mail, thread it, and let you
    reply — built for support and reply-to flows.
  </Card>

  <Card title="Data from inbound mail" img="https://mintcdn.com/dairo/pK0TZ5ICM74nt9cd/images/data-inbound.webp?fit=max&auto=format&n=pK0TZ5ICM74nt9cd&q=85&s=5993efb07c88599e717c3782c5e077c4" width="1000" height="667" data-path="images/data-inbound.webp">
    Give an inbox a schema and incoming email arrives as clean, structured fields.
  </Card>

  <Card title="Real physical letters" img="https://mintcdn.com/dairo/pK0TZ5ICM74nt9cd/images/letters-tracking.webp?fit=max&auto=format&n=pK0TZ5ICM74nt9cd&q=85&s=207780b90de371b0e4ab6394ca7ae0b1" width="1000" height="667" data-path="images/letters-tracking.webp">
    Send a PDF as a printed, posted letter — invoices, contracts, notices — and
    track it from queued to delivered.
  </Card>

  <Card title="Agent-to-agent & chat" img="https://mintcdn.com/dairo/pK0TZ5ICM74nt9cd/images/agent-to-agent.webp?fit=max&auto=format&n=pK0TZ5ICM74nt9cd&q=85&s=cccbaf5d532b8279648ec7ffd0d08d39" width="1000" height="667" data-path="images/agent-to-agent.webp">
    Deliver between Dairo inboxes over the signed `a2a` channel, or send and
    receive through a connected Telegram bot or Slack workspace — the same
    inbox, message, and send calls.
  </Card>

  <Card title="Contacts" img="https://mintcdn.com/dairo/pK0TZ5ICM74nt9cd/images/contacts.webp?fit=max&auto=format&n=pK0TZ5ICM74nt9cd&q=85&s=40e09b019ffc363f4de5ac766dd1f9e0" width="1000" height="667" data-path="images/contacts.webp">
    A cross-channel address book: store recipients once, reach them by handle or
    `@me`, and read a contact's full inbound and outbound history.
  </Card>
</CardGroup>

## How it works

Most integrations follow the same short path.

<Steps>
  <Step title="Verify a domain">
    Register a sending domain and publish the DNS records Dairo gives you, so
    your mail authenticates and lands in the inbox. See
    [Add & verify a domain](/domains/domains).
  </Step>

  <Step title="Send and receive">
    Send email or a letter from an address on your domain. Replies arrive as
    structured [messages and threads](/receiving/messages-and-threads) you can
    read and answer over the same API.
  </Step>

  <Step title="React to events">
    Get a signed [webhook](/webhooks/webhooks) the moment something happens — a
    reply, a delivery, a bounce, or a complaint.
  </Step>
</Steps>

## Core concepts

You'll meet these terms across the docs.

| Concept     | What it is                                                                                                       |
| ----------- | ---------------------------------------------------------------------------------------------------------------- |
| **Domain**  | A domain you verify once, then send and receive from.                                                            |
| **Inbox**   | An address on a verified domain — or a connected bot, workspace, or phone number — that both sends and receives. |
| **Channel** | The medium a message travels over: `email`, `a2a`, `telegram`, or `slack`.                                       |
| **Message** | An inbound or outbound record on a channel, with a status and delivery events, grouped into a thread.            |
| **Contact** | An address-book entry with per-channel handles and a cross-channel history.                                      |
| **Letter**  | A PDF sent as real physical mail, with a status and a delivery timeline.                                         |
| **Webhook** | A signed HTTP call to your app when something happens.                                                           |

[Foundations](/concepts/the-envelope) covers the details every endpoint shares —
response shape, scopes, errors, idempotency, and pagination.

Everything here is available over the REST API at `https://api.dairo.app`,
through [SDKs in nine languages](/sdks/overview), a CLI, and a hosted MCP
server — all authenticated with the same API key.

<Note>
  **For AI agents.** Dairo is agent-native: an agent can hold a real inbox,
  receive inbound mail as structured data, and act through the hosted
  [MCP server](/agent-first/mcp-server)'s typed tools. Start with
  [agent patterns](/agent-first/agent-patterns).
</Note>

## Next steps

<CardGroup cols={2}>
  <Card title="Send your first email" img="https://mintcdn.com/dairo/pK0TZ5ICM74nt9cd/images/quickstart.webp?fit=max&auto=format&n=pK0TZ5ICM74nt9cd&q=85&s=b6e0e3a237080fbb4e0240997255b40f" href="/get-started/quickstart" width="1000" height="667" data-path="images/quickstart.webp">
    The two-minute path from zero to a delivered email.
  </Card>

  <Card title="Explore the API" img="https://mintcdn.com/dairo/pK0TZ5ICM74nt9cd/images/explore-api.webp?fit=max&auto=format&n=pK0TZ5ICM74nt9cd&q=85&s=b716168f034d3753aee3e6c0dd19f186" href="/api-reference" width="1000" height="667" data-path="images/explore-api.webp">
    Every endpoint, with copy-paste requests in each SDK.
  </Card>
</CardGroup>