Barracuda is a free DNSBL of IP addresses known to send spam. Barracuda Networks fights spam and created the BRBL to help stop the spread of spam. Many corporations use Barracuda too. If you send B2B messaging, be on the lookout for this one.
SpamCop determines the origin of unwanted email based on reports from users of their service and passes it along to the relevant Internet service providers.
Unsubscribe Black List, empowers organizations to identify and block the very worst unsubscribe abusers: those that send email to addresses which have been harvested from suppression lists.
Spam and Open Relay Blocking System, Sorbs is another free DNSBL of IP addresses. When it comes to this one, you shouldn’t be worried. Sorbs.net has a ton of IPs on its blacklist, and if you’re on this one, you likely won’t see any effect to your message deliver.
SURBLs are lists of web sites that have appeared in unsolicited messages. Unlike most lists, SURBLs are not lists of message senders..
URIBL is a Realtime URI Blacklist (RHSBL) served via DNS to identify Unsolicitied Bulk and Commercial Email (UCE/UBE) based on the links within the email. URIBL.COM is enabled by default in the popular opensource SpamAssassin.
Free DNS host karma listing servers to provide information to the world about what servers are sending spam, nonspam, or a mix of spam and nonspam.
SARBL - Smart Adaptative Realtime URIBL. SARBL is a dns service anyone can use to filter spams.