The SORBS (Spam and Open Relay Blocking System) provides free access to its DNS-based Block List (DNSBL) to effectively block email from more than 12 million host servers known to disseminate spam, phishing attacks and other forms of malicious email. The list typically includes email servers suspected of sending or relaying spam, servers that have been hacked and hijacked, and those with Trojan infestations. In an attempt to provide preemptive protection, SORBS also lists servers with dynamically allocated IP addresses.
This is what you would see if your IP was listed as a dynamic IP address thus listed on dul.dnsbl.sorbs.net:
Dynamic IP Addresses See: http://www.sorbs.net/lookup.shtml?XXX.XXX.XXX.XXX
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!