private function setConfigOption($option_type, $option_value)
    {
        if ($option_type === 'message_variables') {
            $option_type = 'pass';
        } else if ($option_type === 'attachments') {
            $option_type = 'attach';
        }

        if (!method_exists($this, $option_type)) {
            return false;
        }

        $this->$option_type($option_value);

        return true;
    }