How do block lists work?
The block listing service works as follows. A database of block listed/verified spammers is maintained in a central database on www.spamhaus.org, and BC subscribes to three of their services – SBL, XBL, and PBL. The SBL (Spamhaus Block List) is a real-time database of IP addresses of verified spam sources and is queriable in real-time, allowing email administrators to identify or block incoming connections from IP addresses involved in the sending of unsolicited bulk email. The XBL (Exploits Block List) is a real-time database of IP addresses of illegal 3rd party exploits, including open proxies (HTTP, socks, AnalogX, wingate, etc), worms/viruses with built-in spam engines, and other types of Trojan-horse exploits. The PBL (Policy Block List) is a real-time database of IP addresses that should not be delivering unauthenticated SMTP email to any Internet mail server except those provided specifically by an ISP for that customer’s use BC has a continuous feed from these three block lists
