/**
  * Sends the TAT invitation email to the reference subject.
  *
  * @param string $enquiryId
  * Identifies the reference. Can be either the IRN or the ERN.
  *
  * @return boolean
  * Returns true on success, false otherwise.
  */
 public function sendTatInvitation($enquiryId)
 {
     $returnVal = false;
     $tatManager = new Manager_Referencing_Tat($enquiryId);
     if ($tatManager->isTatApplicable()) {
         $tatMailManager = new Manager_Referencing_TatMail($tatManager->_reference);
         if (!$tatMailManager->getIsTatInvitationSent()) {
             if ($tatMailManager->sendTatInvitation()) {
                 $returnVal = true;
             }
         }
     }
     return $returnVal;
 }