Use Lumail SMTP when an application can only send through SMTP and cannot call `POST /api/v1/emails` directly.

The endpoint is designed for low-volume transactional email: authentication codes, magic links, password resets, account invitations, receipts, and operational notifications. SMTP messages are accepted by the Lumail SMTP adapter, authenticated with a Lumail API token, then queued through the transactional priority lane.

## Connection Settings

| Setting  | Value                                  |
| -------- | -------------------------------------- |
| Host     | `smtp.lumail.io`                       |
| Port     | `587`                                  |
| Security | STARTTLS                               |
| Username | Your organization slug, or any label   |
| Password | A Lumail API token                     |
| From     | An address on a verified Lumail domain |

The password is not your Lumail account password. Create an API token from **Settings -> API Tokens** and store it in your application's secret manager.

## Setup Checklist

1. Verify the sending domain in Lumail.
2. Create a Lumail API token in the same organization.
3. Configure your app to use `smtp.lumail.io` on port `587` with STARTTLS.
4. Use a `From` address on the verified domain.
5. Send one test email before enabling the integration in production.

For the full setup flow, use the [SMTP transactional email tutorial](/docs/tutorials/smtp-transactional-emails).

## Supabase Auth

Supabase Auth custom SMTP can use these values:

```text
Host: smtp.lumail.io
Port: 587
Security: STARTTLS
Username: your-org-slug
Password: lum_your_api_token
Sender email: auth@your-verified-domain.com
```

If your application supports HTTP hooks, prefer [POST /api/v1/emails](/docs/api-reference/api-emails-send). The HTTP API returns structured errors and avoids SMTP/MIME parsing.

## Related Documentation

- [SMTP transactional email tutorial](/docs/tutorials/smtp-transactional-emails) - End-to-end setup for an organization
- [SMTP endpoint reference](/docs/api-reference/smtp) - Response codes, limits, and behavior
- [Create an API token](/docs/tutorials/create-api-token) - Generate the SMTP password
- [Email domains](/docs/domains/email-domains) - Verify the sender domain