1.20.x mail.inc backdrop_mail($module, $key, $to, $language, $params = array(), $reply = NULL, $send = TRUE)

Composes and optionally sends an e-mail message.

Sending an e-mail works with defining an e-mail template (subject, text and possibly e-mail headers) and the replacement values to use in the appropriate places in the template. Processed e-mail templates are requested from hook_mail() from the module sending the e-mail. Any module can modify the composed e-mail message array using hook_mail_alter(). Finally backdrop_mail_system()->mail() sends the e-mail, which can be reused if the exact same composed e-mail is to be sent to multiple recipients.

Finding out what language to send the e-mail with needs some consideration. If you send e-mail to a user, her preferred language should be fine, so use user_preferred_language(). If you send email based on form values filled on the page, there are two additional choices if you are not sending the e-mail to a user on the site. You can either use the language used to generate the page ($language global variable) or the site default language. See language_default(). The former is good if sending e-mail to the person filling the form, the later is good if you send e-mail to an address previously set up (like contact addresses in a contact form).

Taking care of always using the proper language is even more important when sending e-mails in a row to multiple users. Hook_mail() abstracts whether the mail text comes from an administrator setting or is static in the source code. It should also deal with common mail tokens, only receiving $params which are unique to the actual e-mail at hand.

An example:

  function example_notify($accounts) {
    foreach ($accounts as $account) {
      $params['account'] = $account;
      // example_mail() will be called based on the first backdrop_mail() parameter.
      backdrop_mail('example', 'notice', $account->mail, user_preferred_language($account), $params);

  function example_mail($key, &$message, $params) {
    $data['user'] = $params['account'];
    $options['language'] = $message['language'];
    user_mail_tokens($variables, $data, $options);
    switch($key) {
      case 'notice':
        // If the recipient can receive such notices by instant-message, do
        // not send by email.
        if (example_im_send($key, $message, $params)) {
          $message['send'] = FALSE;
        $langcode = $message['language']->langcode;
        $message['subject'] = t('Notification from !site', $variables, array('langcode' => $langcode));
        $message['body'][] = t("Dear !username\n\nThere is new content available on the site.", $variables, array('langcode' => $langcode));

Another example, which uses backdrop_mail() to format a message for sending later:

  $params = array('current_conditions' => $data);
  $to = 'user@example.com';
  $message = backdrop_mail('example', 'notice', $to, $language, $params, FALSE);
  // Only add to the spool if sending was not canceled.
  if ($message['send']) {


$module: A module name to invoke hook_mail() on. The {$module}_mail() hook will be called to complete the $message structure which will already contain common defaults.

$key: A key to identify the e-mail sent. The final e-mail id for e-mail altering will be {$module}_{$key}.

$to: The e-mail address or addresses where the message will be sent to. The formatting of this string must comply with RFC 2822. Some examples are:

$language: Language object to use to compose the e-mail.

$params: Optional parameters to build the e-mail.

string $reply: Optional e-mail address to be used to answer.

$send: If TRUE, backdrop_mail() will call backdrop_mail_system()->mail() to deliver the message, and store the result in $message['result']. Modules implementing hook_mail_alter() may cancel sending by setting $message['send'] to FALSE.

Return value

The $message array structure containing all details of the: message. If already sent ($send = TRUE), then the 'result' element will contain the success indicator of the e-mail, failure being already written to the watchdog. (Success means nothing more than the message being accepted at php-level, which still doesn't guarantee it to be delivered.)


includes/mail.inc, line 119
API functions for processing and sending e-mail.


function backdrop_mail($module, $key, $to, $language, $params = array(), $reply = NULL, $send = TRUE) {
  $from = config_get('system.core', 'site_mail');
  if (empty($from)) {
    $from = ini_get('sendmail_from');

  // Bundle up the variables into a structured array for altering.
  $message = array(
    'id' => $module . '_' . $key,
    'module' => $module,
    'key' => $key,
    'to' => $to,
    'from' => $from,
    'reply-to' => isset($reply) ? $reply : $from,
    'language' => $language,
    'params' => $params,
    'send' => TRUE,
    'subject' => '',
    'body' => array()

  // Build the default headers. Note that the first letter of each word is
  // always capitalized. See: https://tools.ietf.org/html/rfc5322
  $headers = array(
    'MIME-Version' => '1.0',
    'Content-Type' => 'text/plain; charset=UTF-8; format=flowed; delsp=yes',
    'Content-Transfer-Encoding' => '8Bit',
    'X-Mailer' => 'Silkscreen CMS'
  if ($from) {
    // To prevent e-mail from looking like spam, the addresses in the Sender and
    // Return-Path headers should have a domain authorized to use the originating
    // SMTP server.
    $headers['From'] = $headers['Sender'] = $headers['Return-Path'] = $from;
  if ($reply) {
    $headers['Reply-To'] = $reply;
  $message['headers'] = $headers;

  // Build the e-mail (get subject and body, allow additional headers) by
  // invoking hook_mail() on this module. We cannot use module_invoke() as
  // we need to have $message by reference in hook_mail().
  if (function_exists($function = $module . '_mail')) {
    $function($key, $message, $params);

  // Invoke hook_mail_alter() to allow all modules to alter the resulting e-mail.
  backdrop_alter('mail', $message);

  // Retrieve the responsible implementation for this message.
  $system = backdrop_mail_system($module, $key);

  // Format the message body.
  $message = $system->format($message);

  // Optionally send e-mail.
  if ($send) {
    // The original caller requested sending. Sending was canceled by one or
    // more hook_mail_alter() implementations. We set 'result' to NULL, because
    // FALSE indicates an error in sending.
    if (empty($message['send'])) {
      $message['result'] = NULL;
    // Sending was originally requested and was not canceled.
    else {
      $message['result'] = $system->mail($message);
      // Log errors.
      if (!$message['result']) {
        watchdog('mail', 'Error sending e-mail (from %from to %to).', array('%from' => $message['from'], '%to' => $message['to']), WATCHDOG_ERROR);
        backdrop_set_message(t('Unable to send e-mail. Contact the site administrator if the problem persists.'), 'error');

  return $message;