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.

Listing Policy contains entire netblocks of ISP’s that are tolerant of spammers. This means that could potentially have some of the large shared hosting providers listed, such as DreamHost, RackSpace, BlueHost, and GoDaddy. These so called “spam supporters” are added to the list after a “three strikes and you are out” type of policy. After the third spam is seen coming from one of these large ISP’s, their entire range of IP addresses will be added to This often can mean that hundreds of thousands of IP addresses will be contained within this blacklist.