What's DNS Blacklist?
A DNS Blacklist, or DNSBL is a means by which an Internet site may publish a list of IP addresses that some people may want to avoid and in a format which can be easily queried by computer programs on the Internet. The technology is built on top of the Internet Domain Name System, or DNS. DNSBLs are chiefly used to publish lists of addresses linked to spamming. Most mail transport agent (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 names a medium, not any specific list or policy. There has been a good deal of controversy over the past several years over the operation of specific lists, such as the MAPS RBL and SPEWS.