Spam, when it comes down to it, is a genuine threat to the IT infrastructure of any organization. It can be a source of viruses that can infect servers and desktop computers, propagate frighteningly fast and that can compromise confidential company information. Even the biggest companies in the world are vulnerable to these threats and that is why many of them outsource spam control as among their contract IT services.
The majority of email clients (software) includes the ability to setup filters that will automatically perform certain tasks. If you don’t already know how to set up and use Spam Filters, Google It.
DNSBLs (DNS-based Blackhole List, Block List, or Blacklist) are one of the many useful tools used by server administrators in the ongoing war on spam.
The DNSBL’s primary use is to prevent network resources from being wasted on known spam email traffic. In order for a DNSBL to effectively function, it must have a domain name for the list, a server to post it on, and addresses to include on the list. There is no universal DNSBL, however, due to the different thresholds that organizations use to label incoming spam on their respective network(s). Although the listings are used to filter spam, some Internet activists view this as censorship.
This online tool allows you to lookup for blacklisted IP addresses against 60 most active DNSBLs that currently on the internet.
How to Use?
Go to http://dnsbllookup.com
Enter any suspicious IP address that you wanted to check into the form field and press the "LOOKUP" button
An animated loading bar will appear
Be patient, as the lookup may take up to a minute to complete
The status is shown as "Listed" if the IP address appear on any DNS blacklist or "Not Listed" if it isn't blacklisted
Click on various DNSBLs and follow the link to their website for further explanation
Under normal circumstances, if you never send any unsolicited bulk email to anyone or you have not participated in any form of spam campaign, this tool need not be used.