/**
  * Action on pre send event of mailer transport.
  *
  * @param FilterPreSendEvent $event The event
  */
 public function onPreSend(FilterPreSendEvent $event)
 {
     foreach ($this->registry->getTransportFilters() as $filter) {
         if ($filter->supports($event->getTransport(), $event->getMessage(), $event->getMailRendered())) {
             $filter->filter($event->getTransport(), $event->getMessage(), $event->getMailRendered());
         }
     }
 }