RATS-NoPtr is a collection of IP Addresses that have been found sending an abusive amount of connections, or trying too many invalid users at ISP and Telco's mail servers, and are also known to have no reverse DNS, a technique often used by bots and spammers. Email servers should always have reverse DNS entries.
Eg. Server Not Found!
Real email servers have a reverse DNS entry, according to "Best Practices for ISP's and Network Operators". It should reflect the operator of the mail server. And if on top of that, they are sending out a flood of connections, you can probably bet that it is a spammer running a trojan or bot. This represents approximately 30% of the most abusive forms of wasted overhead facing mail servers. Use this to protect your server at a global level, just remember, as in all DNS based checks, if someone looses their DNS server, or for some reason your mail server fails to have a working DNS, you COULD block all email, but this is a normally relatively safe.
A quick check of the database reveals that app. 3000 Class C's have over 50 IP's that have no active reverse DNS and have been engaged in some form of attack against mail servers across North America. Just these 3000 worst offenders add up to almost 3/4 million IP addresses that could be attacking your servers, running dictionary attacks.
You should not need to 'install' anything. Just ensure that your RBL Lookup tool is set to point to 'noptr.spamrats.com'.
Remember, you can ONLY remove your IP from this list, IF you have corrected your reverse DNS entry, which was one of the reasons you got on this list in the first place, to better conform to 'Best Practices'. Make sure that enough time has passed for DNS propagation.
Enter the IP Address you wish to remove: