/**
  * Creates a list of recipients containing all active subscribers.
  *
  * @throws RuntimeExcpetion
  *
  * @return NewsletterRecipientList
  */
 public static function createInstanceActiveSubscribers()
 {
     $recipientList = new self();
     $activeSubscribers = SubscriberPeer::retrieveSubscribed();
     if (!empty($activeSubscribers)) {
         /* @var $eachSubscriber Subscriber */
         foreach ($activeSubscribers as $eachSubscriber) {
             $recipientList->addBcc($eachSubscriber->getSwiftAddress());
         }
         return $recipientList;
     } else {
         throw new RuntimeException('There are no active subscribers.');
     }
 }