Symfony

The mailchannels/mailchannels-php package ships a Symfony Mailer transport. If you already have a Symfony application that builds Symfony\Component\Mime\Email objects and sends them through MailerInterface, you can switch to MailChannels with just a few lines of configuration.

This plugin is optional and lives alongside the rest of the PHP SDK. The plugin itself can only send mail. It doesn’t implement the full API surface (sub-accounts, keys, webhooks, etc.). For those features, use the SDK’s Client directly.

Prerequisites

Before you send your first message, follow the PHP quickstart prerequisite section. This will walk you through creating an account, generating an API key, and adding the required Domain Lockdown and SPF DNS records.

Installation

Install the SDK and the Symfony Mailer component:

composer require mailchannels/mailchannels-php symfony/mailer

The SDK also needs a PSR-18 HTTP client and PSR-17 factories. Symfony HTTP Client + Nyholm PSR-7 is a natural fit for a Symfony project (Guzzle works too, but install one or the other, not both):

composer require symfony/http-client nyholm/psr7

Configuring Symfony

Symfony discovers mailer transports through tagged services. Register the factory in config/services.yaml:

config/services.yaml

services:
    MailChannels\Plugins\Symfony\Transport\MailChannelsTransportFactory:
        tags: ['mailer.transport_factory']

See Symfony’s docs on custom transport factories for background on how this mechanism works.

Point MAILER_DSN at MailChannels

Set the MAILER_DSN environment variable, in your .env file or your environment:

.env

MAILER_DSN=mailchannels+api://${MAILCHANNELS_API_KEY}@default

Scheme: mailchannels or mailchannels+api (both accepted).
DSN user: your MailChannels API key.
DSN host: leave as default for the production API endpoint.

See Symfony’s transport setup docs for more on the DSN format and how it’s typically wired up per-environment.

Sending mail

Once configured, send mail through the standard MailerInterface. No MailChannels-specific code is required for a basic send:

use Symfony\Component\Mailer\MailerInterface;
use Symfony\Component\Mime\Email;

class YourService
{
    public function __construct(private readonly MailerInterface $mailer) {}

    public function sendWelcomeEmail(): void
    {
        $email = (new Email())
            ->from('sender@example.com')
            ->to('recipient@example.com')
            ->subject('Welcome to MailChannels')
            ->text('Plain-text body.')
            ->html('<p>HTML body.</p>');

        $this->mailer->send($email);
    }
}

See Symfony’s docs on creating and sending messages for everything else Email supports (multiple recipients, reply-to, attachments, and so on).

This transport only builds one personalization per message. If you need to send multiple individualized emails in one request, call the SDK’s Client directly instead of going through MailerInterface. See How emails are structured for more information on personalizations.

Control headers

Symfony’s Email object has no equivalent for some MailChannels API features. Reach those instead through custom headers prefixed with x-mailchannels-, set on the Email’s header bag. The x-mailchannels-* headers are stripped before the message is sent, so recipients never see them.

$email->getHeaders()->addTextHeader('x-mailchannels-transactional', 'true');

If the same custom header is added twice, only the last value is used.

Boolean headers accept only the literal strings "true" / "false"; anything else throws Symfony\Component\Mailer\Exception\TransportException. An empty value is treated as unset (falls back to the default).

Header	Description
`x-mailchannels-send-async`	Queue the message (`true`, the default) instead of sending it synchronously (`false`). Equivalent to calling the SDK’s `queue()` vs. `send()`. Queued sends report delivery status via webhooks rather than in the response.
`x-mailchannels-click-tracking-enable`	Enable click tracking.
`x-mailchannels-click-tracking-domain`	Custom domain for click-tracking links. See Custom tracking.
`x-mailchannels-open-tracking-enable`	Enable open tracking.
`x-mailchannels-open-tracking-domain`	Custom domain for open-tracking links. See Custom tracking.
`x-mailchannels-unsubscribe-domain`	Custom domain for unsubscribe links. See Custom tracking.
`x-mailchannels-transactional`	Whether the mail is transactional or non-transactional (marketing, etc.). Affects List-Unsubscribe handling, see Unsubscribe.
`x-mailchannels-dkim-domain`	Domain to use for DKIM signing.
`x-mailchannels-dkim-selector`	Selector to use for DKIM signing.
`x-mailchannels-dkim-private-key`	Private key to use for DKIM signing.
`x-mailchannels-campaign-id`	Campaign that this message is part of.

Each of these corresponds directly to a field on the send endpoint. See that reference for full semantics.

This integration only supports DKIM via the x-mailchannels-dkim-* headers above.If a DKIM-Signature header is already present on the message, the message is rejected, since the provided signature won’t match the message the API constructs.See DKIM signing and key management for information on how MailChannels handles signing and keys.

Reading the result

Synchronous send (x-mailchannels-send-async: false): the sent message’s ID is written back onto Symfony’s SentMessage object, so you can read it after sending.
Queued (default): the API doesn’t return a message ID per call, so Symfony’s own generated message ID is left untouched on SentMessage.

$sentMessage = $this->mailer->send($email);
echo $sentMessage?->getMessageId();

Error handling

Any SDK exception raised while sending (authentication, validation, rate limiting, server errors) is caught and re-thrown as Symfony\Component\Mailer\Exception\TransportException. Access the original exception via $e->getPrevious() to inspect it:

use Symfony\Component\Mailer\Exception\TransportException;

try {
    $this->mailer->send($email);
} catch (TransportException $e) {
    $previous = $e->getPrevious();
    if ($previous instanceof \MailChannels\Exception\RateLimitException) {
        // handle rate limit
    } elseif ($previous instanceof \MailChannels\Exception\ValidationException) {
        // handle validation error
    } else {
        // handle other transport errors
    }
}

Limitations

One personalization per message. No per-recipient template data or per-recipient header overrides through this transport.
No Mustache templating. This transport has no way to use mailchannels’ mustache template rendering. If you need to do so, use Symfony’s Template Support, or use the SDK’s Client directly; see Templates for how.
DKIM only via the MailChannels API, as described above.

Next steps

Read the webhooks guide to learn how to get real-time notifications about email delivery, bounces, and complaints.
Explore the API reference to see what else you can do with the API.

Get Started

API Reference

Authentication & Account Setup

Sending Email

Email Authentication

Webhooks & Delivery Events

Platform & Multi-tenant

Reputation and Abuse Control

Metrics & Monitoring

Operate in production

Migration guides

Integrations

For AI Agents

Prerequisites

Installation

Configuring Symfony

Sending mail

Control headers

Reading the result

Error handling

Limitations

Next steps

​Prerequisites

​Installation

​Configuring Symfony

​Sending mail

​Control headers

​Reading the result

​Error handling

​Limitations

​Next steps

Prerequisites

Installation

Configuring Symfony

Sending mail

Control headers

Reading the result

Error handling

Limitations

Next steps