Sending Emails with Mailer¶

Using a 3rd Party Transport¶

Instead of using your own SMTP server, you can send emails via a 3rd party provider. Mailer supports several - install whichever you want:

Each library includes a Symfony Flex recipe that will add a configuration example to your .env file. For example, suppose you want to use SendGrid. First, install it:

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$ composer require symfony/sendgrid-mailer

You'll now have a new line in your .env file that you can uncomment:

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# .env
MAILER_DSN=sendgrid://[email protected]

The MAILER_DSN isn't a real address: it's a convenient format that offloads most of the configuration work to mailer. The sendgrid scheme activates the SendGrid provider that you just installed, which knows all about how to deliver messages via SendGrid. The only part you need to change is the KEY placeholder.

Each provider has different environment variables that the Mailer uses to configure the actual protocol, address and authentication for delivery. Some also have options that can be configured with query parameters at the end of the MAILER_DSN - like ?region= for Amazon SES or Mailgun. Some providers support sending via http, api or smtp. Symfony chooses the best available transport, but you can force to use one:

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# .env
# force to use SMTP instead of HTTP (which is the default)
MAILER_DSN=sendgrid+smtp://[email protected]

This table shows the full list of available DSN formats for each third party provider:

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# .env
MAILER_DSN=mailgun+https://KEY:[email protected]
MAILER_DSN=mailgun+https://KEY:[email protected]:99

High Availability¶

Symfony's mailer supports high availability via a technique called "failover" to ensure that emails are sent even if one mailer server fails.

A failover transport is configured with two or more transports and the failover keyword:

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MAILER_DSN="failover(postmark+api://[email protected] sendgrid+smtp://[email protected])"

The mailer will start using the first transport. If the sending fails, the mailer won't retry it with the other transports, but it will switch to the next transport automatically for the following deliveries.

Load Balancing¶

Symfony's mailer supports load balancing via a technique called "round-robin" to distribute the mailing workload across multiple transports.

A round-robin transport is configured with two or more transports and the roundrobin keyword:

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MAILER_DSN="roundrobin(postmark+api://[email protected] sendgrid+smtp://[email protected])"

The mailer will start using a randomly selected transport and if it fails, it will retry the same delivery with the next transports until one of them succeeds (or until all of them fail).

TLS Peer Verification¶

By default, SMTP transports perform TLS peer verification. This behavior is configurable with the verify_peer option. Although it's not recommended to disable this verification for security reasons, it can be useful while developing the application or when using a self-signed certificate:

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$dsn = 'smtp://user:[email protected]?verify_peer=0'

Email Addresses¶

All the methods that require email addresses (from(), to(), etc.) accept both strings or address objects:

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// ...
use Symfony\Component\Mime\Address;

$email = (new Email())
    // email address as a simple string
    ->from('[email protected]')

    // email address as an object
    ->from(new Address('[email protected]'))

    // defining the email address and name as an object
    // (email clients will display the name)
    ->from(new Address('[email protected]', 'Fabien'))

    // defining the email address and name as a string
    // (the format must match: 'Name <[email protected]>')
    ->from(Address::create('Fabien Potencier <[email protected]>'))

    // ...
;

Multiple addresses are defined with the addXXX() methods:

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$email = (new Email())
    ->to('[email protected]')
    ->addTo('[email protected]')
    ->addTo('[email protected]')

    // ...
;

Alternatively, you can pass multiple addresses to each method:

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$toAddresses = ['[email protected]', new Address('[email protected]')];

$email = (new Email())
    ->to(...$toAddresses)
    ->cc('[email protected]', '[email protected]')

    // ...
;

Message Headers¶

Messages include a number of header fields to describe their contents. Symfony sets all the required headers automatically, but you can set your own headers too. There are different types of headers (Id header, Mailbox header, Date header, etc.) but most of the times you'll set text headers:

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$email = (new Email())
    ->getHeaders()
        // this header tells auto-repliers ("email holiday mode") to not
        // reply to this message because it's an automated email
        ->addTextHeader('X-Auto-Response-Suppress', 'OOF, DR, RN, NRN, AutoReply');

    // ...
;

Message Contents¶

The text and HTML contents of the email messages can be strings (usually the result of rendering some template) or PHP resources:

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$email = (new Email())
    // ...
    // simple contents defined as a string
    ->text('Lorem ipsum...')
    ->html('<p>Lorem ipsum...</p>')

    // attach a file stream
    ->text(fopen('/path/to/emails/user_signup.txt', 'r'))
    ->html(fopen('/path/to/emails/user_signup.html', 'r'))
;

File Attachments¶

Use the attachFromPath() method to attach files that exist on your file system:

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$email = (new Email())
    // ...
    ->attachFromPath('/path/to/documents/terms-of-use.pdf')
    // optionally you can tell email clients to display a custom name for the file
    ->attachFromPath('/path/to/documents/privacy.pdf', 'Privacy Policy')
    // optionally you can provide an explicit MIME type (otherwise it's guessed)
    ->attachFromPath('/path/to/documents/contract.doc', 'Contract', 'application/msword')
;

Alternatively you can use the attach() method to attach contents from a stream:

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$email = (new Email())
    // ...
    ->attach(fopen('/path/to/documents/contract.doc', 'r'))
;

Embedding Images¶

If you want to display images inside your email, you must embed them instead of adding them as attachments. When using Twig to render the email contents, as explained later in this article, the images are embedded automatically. Otherwise, you need to embed them manually.

First, use the embed() or embedFromPath() method to add an image from a file or stream:

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$email = (new Email())
    // ...
    // get the image contents from a PHP resource
    ->embed(fopen('/path/to/images/logo.png', 'r'), 'logo')
    // get the image contents from an existing file
    ->embedFromPath('/path/to/images/signature.gif', 'footer-signature')
;

The second optional argument of both methods is the image name ("Content-ID" in the MIME standard). Its value is an arbitrary string used later to reference the images inside the HTML contents:

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$email = (new Email())
    // ...
    ->embed(fopen('/path/to/images/logo.png', 'r'), 'logo')
    ->embedFromPath('/path/to/images/signature.gif', 'footer-signature')
    // reference images using the syntax 'cid:' + "image embed name"
    ->html('<img src="cid:logo"> ... <img src="cid:footer-signature"> ...')
;

HTML Content¶

To define the contents of your email with Twig, use the TemplatedEmail class. This class extends the normal Email class but adds some new methods for Twig templates:

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use Symfony\Bridge\Twig\Mime\TemplatedEmail;

$email = (new TemplatedEmail())
    ->from('[email protected]')
    ->to(new Address('[email protected]'))
    ->subject('Thanks for signing up!')

    // path of the Twig template to render
    ->htmlTemplate('emails/signup.html.twig')

    // pass variables (name => value) to the template
    ->context([
        'expiration_date' => new \DateTime('+7 days'),
        'username' => 'foo',
    ])
;

Then, create the template:

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{# templates/emails/signup.html.twig #}
<h1>Welcome {{ email.toName }}!</h1>

<p>
    You signed up as {{ username }} the following email:
</p>
<p><code>{{ email.to[0].address }}</code></p>

<p>
    <a href="#">Click here to activate your account</a>
    (this link is valid until {{ expiration_date|date('F jS') }})
</p>

The Twig template has access to any of the parameters passed in the context() method of the TemplatedEmail class and also to a special variable called email, which is an instance of WrappedTemplatedEmail.

Text Content¶

When the text content of a TemplatedEmail is not explicitly defined, mailer will generate it automatically by converting the HTML contents into text. If you have league/html-to-markdown installed in your application, it uses that to turn HTML into Markdown (so the text email has some visual appeal). Otherwise, it applies the strip_tags PHP function to the original HTML contents.

If you want to define the text content yourself, use the text() method explained in the previous sections or the textTemplate() method provided by the TemplatedEmail class:

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+ use Symfony\Bridge\Twig\Mime\TemplatedEmail;

$email = (new TemplatedEmail())
    // ...

    ->htmlTemplate('emails/signup.html.twig')
+     ->textTemplate('emails/signup.txt.twig')
    // ...
;

Embedding Images¶

Instead of dealing with the <img src="cid: ..."> syntax explained in the previous sections, when using Twig to render email contents you can refer to image files as usual. First, to simplify things, define a Twig namespace called images that points to whatever directory your images are stored in:

Now, use the special email.image() Twig helper to embed the images inside the email contents:

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{# '@images/' refers to the Twig namespace defined earlier #}
<img src="{{ email.image('@images/logo.png') }}" alt="Logo">

<h1>Welcome {{ email.toName }}!</h1>
{# ... #}

Inlining CSS Styles¶

Designing the HTML contents of an email is very different from designing a normal HTML page. For starters, most email clients only support a subset of all CSS features. In addition, popular email clients like Gmail don't support defining styles inside <style> ... </style> sections and you must inline all the CSS styles.

CSS inlining means that every HTML tag must define a style attribute with all its CSS styles. This can make organizing your CSS a mess. That's why Twig provides a CssInlinerExtension that automates everything for you. Install it with:

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$ composer require twig/extra-bundle twig/cssinliner-extra

The extension is enabled automatically. To use it, wrap the entire template with the inline_css filter:

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{% apply inline_css %}
    <style>
        {# here, define your CSS styles as usual #}
        h1 {
            color: #333;
        }
    </style>

    <h1>Welcome {{ email.toName }}!</h1>
    {# ... #}
{% endapply %}

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{% apply inline_css(source('@css/email.css')) %}
    <h1>Welcome {{ username }}!</h1>
    {# ... #}
{% endapply %}

Rendering Markdown Content¶

Twig provides another extension called MarkdownExtension that lets you define the email contents using Markdown syntax. To use this, install the extension and a Markdown conversion library (the extension is compatible with several popular libraries):

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# instead of league/commonmark, you can also use erusev/parsedown or michelf/php-markdown
$ composer require twig/extra-bundle twig/markdown-extra league/commonmark

The extension adds a markdown_to_html filter, which you can use to convert parts or the entire email contents from Markdown to HTML:

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{% apply markdown_to_html %}
    Welcome {{ email.toName }}!
    ===========================

    You signed up to our site using the following email:
    `{{ email.to[0].address }}`

    [Click here to activate your account]({{ url('...') }})
{% endapply %}

Inky Email Templating Language¶

Creating beautifully designed emails that work on every email client is so complex that there are HTML/CSS frameworks dedicated to that. One of the most popular frameworks is called Inky. It defines a syntax based on some HTML-like tags which are later transformed into the real HTML code sent to users:

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<!-- a simplified example of the Inky syntax -->
<container>
    <row>
        <columns>This is a column.</columns>
    </row>
</container>

Twig provides integration with Inky via the InkyExtension. First, install the extension in your application:

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$ composer require twig/extra-bundle twig/inky-extra

The extension adds an inky_to_html filter, which can be used to convert parts or the entire email contents from Inky to HTML:

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{% apply inky_to_html %}
    <container>
        <row class="header">
            <columns>
                <spacer size="16"></spacer>
                <h1 class="text-center">Welcome {{ email.toName }}!</h1>
            </columns>

            {# ... #}
        </row>
    </container>
{% endapply %}

You can combine all filters to create complex email messages:

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{% apply inky_to_html|inline_css(source('@css/foundation-emails.css')) %}
    {# ... #}
{% endapply %}

This makes use of the css Twig namespace we created earlier. You could, for example, download the foundation-emails.css file directly from GitHub and save it in assets/styles.

Signing Messages¶

When signing a message, a cryptographic hash is generated for the entire content of the message (including attachments). This hash is added as an attachment so the recipient can validate the integrity of the received message. However, the contents of the original message are still readable for mailing agents not supporting signed messages, so you must also encrypt the message if you want to hide its contents.

You can sign messages using either S/MIME or DKIM. In both cases, the certificate and private key must be PEM encoded, and can be either created using for example OpenSSL or obtained at an official Certificate Authority (CA). The email recipient must have the CA certificate in the list of trusted issuers in order to verify the signature.

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use Symfony\Component\Mime\Crypto\SMimeSigner;
use Symfony\Component\Mime\Email;

$email = (new Email())
    ->from('[email protected]')
    // ...
    ->html('...');

$signer = new SMimeSigner('/path/to/certificate.crt', '/path/to/certificate-private-key.key');
// if the private key has a passphrase, pass it as the third argument
// new SMimeSigner('/path/to/certificate.crt', '/path/to/certificate-private-key.key', 'the-passphrase');

$signedEmail = $signer->sign($email);
// now use the Mailer component to send this $signedEmail instead of the original email

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use Symfony\Component\Mime\Crypto\DkimSigner;
use Symfony\Component\Mime\Email;

$email = (new Email())
    ->from('[email protected]')
    // ...
    ->html('...');

// first argument: same as openssl_pkey_get_private(), either a string with the
// contents of the private key or the absolute path to it (prefixed with 'file://')
// second and third arguments: the domain name and "selector" used to perform a DNS lookup
// (the selector is a string used to point to a specific DKIM public key record in your DNS)
$signer = new DkimSigner('file:///path/to/private-key.key', 'example.com', 'sf');
// if the private key has a passphrase, pass it as the fifth argument
// new DkimSigner('file:///path/to/private-key.key', 'example.com', 'sf', [], 'the-passphrase');

$signedEmail = $signer->sign($email);
// now use the Mailer component to send this $signedEmail instead of the original email

// DKIM signer provides many config options and a helper object to configure them
use Symfony\Component\Mime\Crypto\DkimOptions;

$signedEmail = $signer->sign($email, (new DkimOptions())
    ->bodyCanon('relaxed')
    ->headerCanon('relaxed')
    ->headersToIgnore(['Message-ID'])
    ->toArray()
);

Encrypting Messages¶

When encrypting a message, the entire message (including attachments) is encrypted using a certificate. Therefore, only the recipients that have the corresponding private key can read the original message contents:

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use Symfony\Component\Mime\Crypto\SMimeEncrypter;
use Symfony\Component\Mime\Email;

$email = (new Email())
    ->from('[email protected]')
    // ...
    ->html('...');

$encrypter = new SMimeEncrypter('/path/to/certificate.crt');
$encryptedEmail = $encrypter->encrypt($email);
// now use the Mailer component to send this $encryptedEmail instead of the original email

You can pass more than one certificate to the SMimeEncrypter constructor and it will select the appropriate certificate depending on the To option:

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$firstEmail = (new Email())
    // ...
    ->to('[email protected]');

$secondEmail = (new Email())
    // ...
    ->to('[email protected]');

// the second optional argument of SMimeEncrypter defines which encryption algorithm is used
// (it must be one of these constants: https://www.php.net/manual/en/openssl.ciphers.php)
$encrypter = new SMimeEncrypter([
    // key = email recipient; value = path to the certificate file
    '[email protected]' => '/path/to/first-certificate.crt',
    '[email protected]' => '/path/to/second-certificate.crt',
]);

$firstEncryptedEmail = $encrypter->encrypt($firstEmail);
$secondEncryptedEmail = $encrypter->encrypt($secondEmail);

Disabling Delivery¶

While developing (or testing), you may want to disable delivery of messages entirely. You can do this by using null://null as the mailer DSN, either in your .env configuration files or in the mailer configuration file (e.g. in the dev or test environments):

Always Send to the same Address¶

Instead of disabling delivery entirely, you might want to always send emails to a specific address, instead of the real address: