Спасибо Калле за то, что нашли время, чтобы изучить мой запрос. Но вот ниже я, наконец, получил ответ на мой вопрос ->http://www.dnsstuff.com/reverse-dns-faq
Думал, что это стоило бы делиться здесь:
Очень распространенный миф:
* Myth: If you have a reverse DNS entry listed in your DNS server, you have reverse DNS properly set up.
Fact: This is often not the case. You need TWO things in order to have your DNS set up properly:
o 1. Your DNS servers (or your ISP's) MUST have the reverse DNS entries set up ("25.2.0.192.in-addr.arpa. PTR host.example.com").
o 2. AND your ISP or bandwidth provider MUST set up the reverse DNS on their end, so that DNS resolvers around the world will know that your DNS servers are the ones to go to when looking up the reverse DNS for your IP addresses.