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SDKs

PHP

Use the official Lettermint PHP SDK to send email from a PHP application. If you use Laravel, use the Laravel mail driver. If you use Symfony Mailer, use the Symfony guide. See SDKs and integrations for other packages.

Requirements

Before you start you need:

• PHP 8.2 or newer with Composer. The SDK uses Guzzle 7.15.2 or newer, or Guzzle 8, which Composer installs for you.
• A Lettermint account with a verified sending domain
• A Project API token from your project settings

If your domain is not verified yet, follow the domain setup guide first so your mail reaches the inbox instead of the spam folder.

1. Installation

Install the SDK via Composer:

Code
composer require lettermint/lettermint-php

2. Send your first email

Create the client with your Project API token as the sendingToken:

Code
<?php

require_once 'vendor/autoload.php';

use Lettermint\Lettermint;

$lettermint = new Lettermint(sendingToken: getenv('LETTERMINT_PROJECT_TOKEN'));

The client stores nothing about a message, so create it once and share it across your app, also in long-running workers such as Octane, Horizon, or Symfony Messenger. You can also pass the token as a string, as in new Lettermint($token).

Send your first email:

Code
$response = $lettermint->emails->send([
    'from' => 'John Doe <john@yourdomain.com>',
    'to' => ['recipient@example.com'],
    'subject' => 'Hello from Lettermint!',
    'text' => 'Hello! This is a test email.',
]);

echo "Email sent with ID: " . $response->message_id;

emails->send() takes the message in the API's format, for example reply_to and scheduled_at. The to, cc, and bcc fields are arrays.

3. Email features

The examples in this section use $lettermint->emails->compose(), a fluent builder. Every setter returns a new builder and leaves the original unchanged, so one builder is safe to share and reuse. Keep the value that a setter returns when you build an email over several statements:

Code
$draft = $lettermint->emails->compose()
    ->from('John Doe <john@yourdomain.com>')
    ->to('recipient@example.com')
    ->subject('Your invoice');

if ($copyAccountant) {
    $draft = $draft->cc('accountant@yourdomain.com');
}

$draft->html('<p>Your invoice is ready.</p>')->send();

Each builder example is equivalent to an array passed to $lettermint->emails->send(). Use whichever reads better.

Basic email

Send a simple text or HTML email:

Code
$lettermint->emails->compose()
    ->from('John Doe <john@yourdomain.com>')
    ->to('recipient@example.com')
    ->subject('Your account is ready!')
    ->html('<h1>Welcome!</h1><p>Thanks for signing up.</p>')
    ->text('Welcome! Thanks for signing up.')
    ->send();

Multiple recipients

Send to multiple recipients using CC and BCC:

Code
$lettermint->emails->compose()
    ->from('John Doe <john@yourdomain.com>')
    ->to('user1@example.com', 'user2@example.com')
    ->cc('manager@yourdomain.com')
    ->bcc('archive@yourdomain.com')
    ->subject('Monthly Newsletter')
    ->html('<h1>This Month\'s Updates</h1>')
    ->send();

Custom headers and reply-to

Add custom headers and set reply-to addresses:

Code
$lettermint->emails->compose()
    ->from('support@yourdomain.com')
    ->to('customer@example.com')
    ->replyTo('help@yourdomain.com')
    ->subject('Support Ticket #12345')
    ->headers([
        'X-Priority' => '1',
        'X-Ticket-ID' => '12345'
    ])
    ->html('<p>Your support ticket has been updated.</p>')
    ->send();

Metadata

Add metadata for tracking and webhook payloads:

Code
$lettermint->emails->compose()
    ->from('notifications@yourdomain.com')
    ->to('user@example.com')
    ->subject('Order Confirmation')
    ->metadata([
        'order_id' => '12345',
        'customer_id' => 'cust_789',
        'campaign' => 'order_confirmation'
    ])
    ->html('<p>Your order has been confirmed.</p>')
    ->send();

Tags

Categorize emails for filtering and analytics:

Code
$lettermint->emails->compose()
    ->from('alerts@yourdomain.com')
    ->to('admin@example.com')
    ->subject('System Alert')
    ->tags([
        ['name' => 'category', 'value' => 'system-alerts'],
        ['name' => 'environment', 'value' => 'production'],
    ])
    ->html('<p>Critical system alert detected.</p>')
    ->send();

Route selection

Direct emails to specific routes within your project:

Code
$lettermint->emails->compose()
    ->from('notifications@yourdomain.com')
    ->to('user@example.com')
    ->subject('Welcome!')
    ->route('transactional')
    ->html('<p>Welcome to our platform.</p>')
    ->send();

Scheduling

Deliver an email later with scheduledAt(). It takes a DateTimeInterface, an ISO 8601 string, or English such as tomorrow 9am:

Code
$result = $lettermint->emails->compose()
    ->from('notifications@yourdomain.com')
    ->to('user@example.com')
    ->subject('Your trial ends tomorrow')
    ->text('Your trial ends tomorrow.')
    ->scheduledAt(new DateTimeImmutable('+1 day'))
    ->send();

See Scheduling for rescheduling and cancelling.

Idempotency

Pass an idempotency key so a retry never sends the same email twice. If a request with the same key is repeated within the idempotency window, Lettermint returns the original result instead of sending again. The key is an argument of the call that sends the email:

Code
$lettermint->emails->compose()
    ->from('notifications@yourdomain.com')
    ->to('user@example.com')
    ->subject('Order Confirmation')
    ->html('<p>Your order has been confirmed.</p>')
    ->send(idempotencyKey: 'order-confirmation-12345');

emails->send($message, idempotencyKey: …) and emails->sendBatch($messages, idempotencyKey: …) take the same argument. The key applies only to that call, and the SDK never retries on its own.

File attachments

Attach files to your emails. Attachment takes raw bytes and base64-encodes them for you:

Code
use Lettermint\Attachment;

$lettermint->emails->compose()
    ->from('invoices@yourdomain.com')
    ->to('customer@example.com')
    ->subject('Your Invoice')
    ->html('<p>Please find your invoice attached.</p>')
    ->attach(Attachment::fromPath('/path/to/document.pdf', filename: 'invoice.pdf', contentType: 'application/pdf'))
    ->send();

Use new Attachment($filename, $bytes, $contentType) for content in memory, or Attachment::fromBase64() for content that is already base64. To show an attachment inside the HTML body, set contentId and reference it as cid: in the markup. See Inline images.

Batch sending

Send up to 500 emails in one request. The list can mix arrays and builders, and the result has one SendMailResponse per email, in order:

Code
$base = $lettermint->emails->compose()
    ->from('John Doe <john@yourdomain.com>')
    ->subject('Your weekly summary');

$results = $lettermint->emails->sendBatch([
    ['from' => 'John Doe <john@yourdomain.com>', 'to' => ['user1@example.com'], 'subject' => 'Hi', 'text' => 'Hello'],
    $base->to('user2@example.com')->text('Your summary is ready.'),
], idempotencyKey: 'weekly-summary-2026-10-05');

echo $results[0]->message_id;

4. Send an order confirmation

A real transactional send usually pulls several of these features together. This example sends a receipt with an HTML and plain-text body, tags it for analytics, attaches the order and customer IDs as metadata, and uses an idempotency key so a retry never emails the customer twice:

order-confirmation.php
<?php

require_once 'vendor/autoload.php';

use Lettermint\Lettermint;

$lettermint = new Lettermint(sendingToken: getenv('LETTERMINT_PROJECT_TOKEN'));

// $order comes from your application (database, cart, etc.)
$order = [
    'id' => 'ORD-12345',
    'number' => '12345',
    'total' => '€49.00',
    'customer_email' => 'customer@example.com',
    'customer_id' => 'cust_789',
];

$response = $lettermint->emails->compose()
    ->from('Acme Store <orders@yourdomain.com>')
    ->to($order['customer_email'])
    ->replyTo('support@yourdomain.com')
    ->subject("Order {$order['number']} confirmed")
    ->html("<h1>Thanks for your order</h1><p>Order {$order['number']} totalling {$order['total']} is confirmed.</p>")
    ->text("Thanks for your order. Order {$order['number']} totalling {$order['total']} is confirmed.")
    ->tags([['name' => 'type', 'value' => 'order-confirmation']])
    ->metadata([
        'order_id' => $order['id'],
        'customer_id' => $order['customer_id'],
    ])
    ->route('transactional')
    ->send(idempotencyKey: "order-confirmation-{$order['id']}");

echo "Order confirmation sent: " . $response->message_id;

The metadata you attach here travels with every webhook event for the message, so a later delivery or bounce maps straight back to the order in your database.

5. Response

Code
$response = $lettermint->emails->compose()
    ->from('John Doe <john@yourdomain.com>')
    ->to('recipient@example.com')
    ->subject('Test')
    ->text('Hello!')
    ->send();

echo $response->message_id; // Email ID
echo $response->status;     // Current status

6. Handle errors

Every exception the SDK throws extends Lettermint\Exceptions\LettermintException. API errors extend ApiException, which carries status, errorCode, and the message. Catch the subclasses you want to handle:

Code
use Lettermint\Exceptions\ApiException;
use Lettermint\Exceptions\RateLimitException;
use Lettermint\Exceptions\TimeoutException;
use Lettermint\Exceptions\ValidationException;

try {
    $lettermint->emails->send($message, idempotencyKey: $key);
} catch (ValidationException $e) {
    error_log($e->getMessage() . ' ' . json_encode($e->errors));
} catch (RateLimitException $e) {
    sleep($e->retryAfter ?? 1); // then retry with the same idempotency key
} catch (TimeoutException $e) {
    // The outcome is unknown. Retry with the same idempotency key.
} catch (ApiException $e) {
    error_log("{$e->status} {$e->errorCode} {$e->getMessage()}");
}

The SDK never retries on its own. Reuse the same idempotency key when you retry so the customer gets one email. Other exceptions include AuthenticationException, PermissionException, NotFoundException, ConflictException, ServerException, ConnectionException, LettermintConfigException for a missing token, and LettermintValidationException when the SDK rejects a request before it sends it.

Track delivery, opens, and bounces

Sending is only half of a transactional setup. To see what happens after a message leaves your app, combine the SDK with Lettermint's platform features:

• Email tracking records opens and clicks, with bot filtering so your metrics stay accurate.
• Webhooks push delivery, bounce, and complaint events to your server in real time, so you can update order records or suppress bad addresses. The SDK verifies each delivery with (new Webhook($secret))->verify($rawBody, $headers). See Webhook signatures.
• Test addresses let you trigger a hard or soft bounce on demand while you build and verify your webhook handler.

Tracking is configured per route, so turn it on for the route your app sends through, then read the results from your dashboard or your webhook endpoint.

FAQ

Does the SDK work with Laravel or another framework?

The SDK works in any PHP project, including Symfony and plain PHP. If you use Laravel, install the dedicated Laravel mail driver instead, which integrates with the Mail facade, Mailables, and queues rather than calling the SDK directly.

Which PHP versions are supported?

PHP 8.2 or newer. Install the SDK with a single composer require lettermint/lettermint-php. CI runs the SDK on PHP 8.2 to 8.5.

How do I stop the same email being sent twice?

Pass an idempotencyKey argument to send() or sendBatch(), derived from a stable ID such as an order number. A repeated request with the same key returns the original result instead of sending again. See the idempotency documentation.

Is Lettermint email GDPR compliant and EU-hosted?

Yes. Lettermint runs exclusively on European infrastructure and processes email in line with GDPR, so transactional mail from your PHP app is handled inside the EU.

How do I track opens, clicks, and bounces?

Enable tracking on your route and subscribe to webhooks to receive delivery, open, and bounce events. Use the test addresses to simulate bounces while you build your handler.

Next steps