private function buildMetadataProperties(PhabricatorMetaMTAMail $mail)
 {
     $viewer = $this->getViewer();
     $properties = id(new PHUIPropertyListView())->setUser($viewer);
     $properties->addProperty(pht('Message PHID'), $mail->getPHID());
     $details = $mail->getMessage();
     if (!strlen($details)) {
         $details = phutil_tag('em', array(), pht('None'));
     }
     $properties->addProperty(pht('Status Details'), $details);
     $actor_phid = $mail->getActorPHID();
     if ($actor_phid) {
         $actor_str = $viewer->renderHandle($actor_phid);
     } else {
         $actor_str = pht('Generated by Phabricator');
     }
     $properties->addProperty(pht('Actor'), $actor_str);
     $related_phid = $mail->getRelatedPHID();
     if ($related_phid) {
         $related = $viewer->renderHandle($mail->getRelatedPHID());
     } else {
         $related = phutil_tag('em', array(), pht('None'));
     }
     $properties->addProperty(pht('Related Object'), $related);
     return $properties;
 }