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Email spam continues to inundate mailboxes. Mailserver adminstrators have found that the most efficient way to fight spam is by blocking the IP addresses of the servers that originate the spam. This led to the use of Domain Name System Blackhole Lists (DNSBLs). While the most common focus of DNSBLs is spam, others focus on hacking, malware, etc.
There are two types of Blacklists: Ip-based email blocking, which is done by IP servers, and the less common, but increasingly popular, domain-based email blocking, performed by domain name hosts. There are three main public domain blacklists: Spamhaus, SURBL, and URIBL. Spamhaus domains drop out of the blacklist automatically if they aren't flagged for some period of time. MXToolbox SURBL is relatively easy to get off by requesting removal. |