The Spam and Open Relay Blocking System
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. SORBS maintains 17 distinct DNSBL zones.
dnsbl.sorbs.net is SORBS primary zone, and contains all other zones. Due to the aggressive nature of some of the zones, it may not be wise to use dnsbl.sorbs.net until you are completely familiar with each of the sub zones contained within.