RBL = Real-time Blackhole List

The Real-time Block List (RBL) is a real-time database of IP addresses of spam-sources, including known spammers, spam gangs, spam operations and spam support services.

The database is kept updated every day, around the clock, by RBL project team members around the world.

How much spam will the RBL block for me?
 It depends on many factors: how many domains one hosts, how many email addresses the domains have, how many email addresses have been harvested by spammers or pulled out by dictionary attacks, geographic "ccTLDs", and other spam-profile factors.

Current numbers show the RBL's can stop, on average, about 50-70% of incoming spam.

How often is the RBL updated?

The RBL DNS zone is rebuilt and reloaded every 15 minutes, 24/7, to ensure that new spam problems are swiftly blocked and that fixed problems are swiftly removed. For high redundancy there are over 40 public mirrors located in many nations around the world.