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

# Send via SMTP relay

> Send transactional email through Mailercloud's SMTP relay from any framework, CMS, or legacy system — no code changes beyond SMTP settings.

If your application already speaks SMTP (WordPress, Laravel, legacy systems, CRMs), you can send through Mailercloud without integrating the HTTP API — just point your SMTP settings at the relay.

## Connection settings

| Setting        | Value                              |
| -------------- | ---------------------------------- |
| Host           | `smtp-relay.mailercloud.com`       |
| Ports          | `587`, `2525`, or `465`            |
| Authentication | `AUTH PLAIN` — username + password |

## Credentials

Switch to the **Transactional Email platform** (toggle in the sidebar), then open **Settings → SMTP Configuration** to view your host, username, and password. Use **Generate new password** to create or rotate the password.

<Warning>
  Generating a new password invalidates the previous one immediately — update all systems using the old credentials.
</Warning>

## Tracking headers

Control tracking per message with custom SMTP headers:

| Header                  | Purpose                                          |
| ----------------------- | ------------------------------------------------ |
| `mld-track-opens`       | `true`/`false` — enable or disable open tracking |
| `mld-track-inbox`       | `true`/`false` — enable inbox-placement tracking |
| `mld-track-campaign-id` | Group sends under a campaign ID for reporting    |

## Security & delivery extras

* **IP Allowed List** — restrict which IP addresses may send through your account (single IPs, ranges, or wildcards). If unset, all IPs are allowed.
* **Webhooks** — receive real-time events for transactional sends: Sent, Delivery, Bounce, Spam, Open. See [Set up webhooks](/guides/webhooks).

## Example (Laravel `.env`)

```ini theme={null}
MAIL_MAILER=smtp
MAIL_HOST=smtp-relay.mailercloud.com
MAIL_PORT=587
MAIL_USERNAME=your-smtp-username
MAIL_PASSWORD=your-smtp-password
MAIL_FROM_ADDRESS=orders@yourdomain.com
```

## SMTP vs HTTP API — which to use?

|                                            | SMTP relay                                  | [HTTP Email API](/api-reference/email/send-email)              |
| ------------------------------------------ | ------------------------------------------- | -------------------------------------------------------------- |
| Setup                                      | Config change only                          | Small code integration                                         |
| Per-recipient personalization (mail merge) | ❌ Not supported                             | ✅ [`/email-api`](/api-reference/email/send-personalized-email) |
| Best for                                   | Existing apps, CMS plugins, quick migration | New integrations, personalization, richer control              |

The sender domain must be [verified](/authentication) on your account in either case.