This is one of a group of RBL's from blockedservers.com This is an RBL with a colorful website. Unfortunatly there is not much information on it's inner workings and how each list is working. Presumably this list contains SPAMers. rbl.blockedservers.com looks like the main list of the service.
Is the information on our site wrong or incomplete? You don't want us to monitor your blacklist? Or do you operate a similar blacklist? We would like to hear from you!
We keep some statistics on blacklists. Below is the graph for spam.rbl.blockedservers.com. We test blacklists by asking them to respond to known IP's that are blacklisted and known IP's that can't be blacklisted. Not every blacklist has such IP's, we test them with what is possible. We keep if we get any response or error messages and the response duration. Lower response times are better. These statistics may be useful for email server administrators to pick which blacklist to use.