Chris@0: /**
Chris@0:  * Implements hook_mail_alter().
Chris@0:  */
Chris@0: function {{ machine_name }}_mail_alter(&$message) {
Chris@0:   if ($message['id'] == 'modulename_messagekey') {
Chris@0:     if (!example_notifications_optin($message['to'], $message['id'])) {
Chris@0:       // If the recipient has opted to not receive such messages, cancel
Chris@0:       // sending.
Chris@0:       $message['send'] = FALSE;
Chris@0:       return;
Chris@0:     }
Chris@0:     $message['body'][] = "--\nMail sent out from " . variable_get('site_name', t('Drupal'));
Chris@0:   }
Chris@0: }