/** Handles the signal, resets the cache */
 @Override
 public void handle(Signal signal) {
   ZimbraLog.milter.info("Received Signal: %s", signal.getName());
   ZimbraLog.milter.info("Begin ACL cache invalidation");
   PermissionCache.invalidateAllCache();
   ZimbraLog.milter.info("ACL cache successfully cleared");
 }