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

# Sending via SMTP

> Connect an SMTP-compatible app or mail client to Sendmux.

Use SMTP when an existing application, plugin, or mail client already supports SMTP delivery.

<Info>
  The SMTP password is your `smx_mbx_` send-only key, mailbox password, or owner-approved Sending-resource `smx_agent_` token.
  Routing still follows that key or mailbox scope.
</Info>

<Warning>
  Managed Amazon SES is for transactional email only. Use your own provider for
  marketing, newsletters, or bulk promotional sends.
</Warning>

## Connection details

| Setting            | Value                                                                                                  |
| ------------------ | ------------------------------------------------------------------------------------------------------ |
| **Host**           | `smtp.sendmux.ai`                                                                                      |
| **Port**           | `587` with STARTTLS, or `2525` with STARTTLS                                                           |
| **Username**       | Any value, such as `smtpuser`                                                                          |
| **Password**       | Your `smx_mbx_` send-only key, mailbox password, or owner-approved Sending-resource `smx_agent_` token |
| **Authentication** | `LOGIN` or `PLAIN`                                                                                     |

## Test with swaks

```bash theme={null}
swaks --to user@example.com \
  --from hello@example.com \
  --server smtp.sendmux.ai:587 \
  --auth LOGIN \
  --auth-user smtpuser \
  --auth-password "smx_mbx_your_key_here" \
  --tls \
  --header "Subject: Test email" \
  --body "Hello from Sendmux"
```

## SMTP vs HTTP

| Need                         | Use      |
| ---------------------------- | -------- |
| Existing SMTP-only tool      | SMTP     |
| New application integration  | HTTP API |
| Batch sending                | HTTP API |
| Built-in retry protection    | HTTP API |
| Native MIME message handling | SMTP     |

## What happens next

Successful SMTP sends appear in **Logs** like HTTP sends. Use the message ID, sender, recipient, status, provider, and timestamp to trace delivery.

## Related guides

<Columns cols={2}>
  <Card title="Send by HTTP" icon="code" href="/docs/guides/sending-via-http">
    Use the API for new integrations and batch sends.
  </Card>

  <Card title="API keys" icon="key" href="/docs/guides/api-keys">
    Create the credentials used as SMTP passwords.
  </Card>

  <Card title="Delivery logs" icon="scroll-text" href="/docs/guides/dashboard-logs">
    Search and export SMTP delivery results.
  </Card>
</Columns>