Reverse DNS is a process of resolving an IP address into a domain name, it’s just as DNS resolves domain names into associated IP addresses. Reverse DNS ensure you that you will not encounter any problems with most of the Enterprise Management Systems, IRC,  r-commands,  network backup system or your SMTP server.  In addition, one of the applications is being used for reverse DNS that work as a spam filter which determine whether the IP address of the incoming message matches an authenticated domain name or not and if in case it doesn’t match,  the spam filter  block the message.  Normally, when a spammer try to use an invalid IP address, and when that IP doesn’t match the domain name, a reverse DNS lookup program inputs IP addresses of incoming messages to a DNS database. If no valid name is found to match the IP address, the server blocks that message.

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