private function deepMxCheck(array $value = []): bool
    {
        $isValid = false;
        foreach ($value as $host => $weight) {
            $res = $this->isReserved($host);
            if (!$res && (\checkdnsrr($host, 'A') || \checkdnsrr($host, 'AAAA') || \checkdnsrr($host, 'A6'))) {
                $isValid = true;
                break;
            }
        }
        return $isValid;
    }