code: protected function throttleDataRead()
      {
          if ($this->throttleData) {
              // already imported
              return;
          }
          $throttleData = array();
          if ($this->cfg['emailThrottleRead'] && \is_callable($this->cfg['emailThrottleRead'])) {
              $throttleData = \call_user_func($this->cfg['emailThrottleRead']);
          } elseif ($this->cfg['emailThrottleFile'] && \is_readable($this->cfg['emailThrottleFile'])) {
              $throttleData = \file_get_contents($this->cfg['emailThrottleFile']);
              $throttleData = \json_decode($throttleData, true);
          }
          if (!\is_array($throttleData)) {
              $throttleData = array();
          }
          $this->throttleData = \array_merge(array(
              'tsGarbageCollection' => \time(),
              'errors' => array(),
          ), $throttleData);
          return;
      }
docs: Load & populate $this->throttleData if not alrady imported
  
  Uses cfg[emailThrottleRead] callable if set, otherwise, reads from cfg['emailThrottleFile']
  
  @return void