protected function doCallback($isSent, $to, $cc, $bcc, $subject, $body, $from, $extra)
    {
        if (!empty($this->action_function) and is_callable($this->action_function)) {
            call_user_func($this->action_function, $isSent, $to, $cc, $bcc, $subject, $body, $from, $extra);
        }
    }