A DNSBL (DNS-based Blackhole List, Block List, or Blacklist; see below) is list of IP addresses published through the Internet Domain Name Service in a particular format. DNSBLs are most often used to publish the addresses of computers or networks linked to spamming; most mail server software can be configured to reject or flag messages which have been sent from a site listed on one or more such lists. "DNSBL" is a software mechanism, rather than a specific list or policy. There are dozens of DN… (More on Dnsbl)