Email Configuration

Falcon mailing functionality is placed in falcon_mail module. The module provides a plugin for Drupal mail system with a formatter that can wrap emails into HTML templates and replace dynamic tokens.

You can change formatter on admin/config/system/mailsystem page.

You can configure you email with several params. Example

$to = $order->getEmail();
$langcode = 'en';
$reply = NULL;
$send = TRUE;

$params = [];
$params['from'] = 'your_email@example.com'
$params['subject'] = "Message subject";
$params['body'] = "<div> Html message body </div>";
$params['headers'] = ['Content-Type' => 'text/html'];   # Enable html. You can pass any headers.
$params['render_tokens']['commerce_order'] = $order;    # Array 'render_tokens' contains variables for token replacement.
$params['token_options'] = [                            # Array 'token_options' contains options for token replaceement.
    'langcode' => $langcode,
    'callback' => 'callback_function'
];
$params['replace_tokens'] = TRUE;                       # Enable replacement tokens.
$params['theme_template'] = "<div> #$#BODY#$# </div>"   # The template where will be replaced #$#BODY#$# on $messsage['body'].

\Drupal::service('plugin.manager.mail')->mail('your_module', 'your_mail_key', $to, $langcode, $params, $reply, $send);

The theme_template param can use the #$#BODY#$# variable for wrap an another html to theme_template html. You can also find an example of working in the falcon_donation module.