What are DNS blacklists?
DNS blacklists are lists of domains that are known to originate Spam. Many anti-spam software programs use these lists to control Spam by refusing any email that originates from one of these domains. DNS blacklists are usually maintained by anti-spam organizations or by individuals with an intense dislike for Spam. The difficulty with DNS blacklists is the need for objectivity in deciding when to blacklist a domain. In order to know that a domain is producing Spam, the offence must be reported. Reporting Spam without any anti-abuse mechanism in place, however, leaves nothing to stop people from getting servers added to a DNS blacklist out of malice. The obvious solution would be to require a minimum number of reported incidents before blacklisting a server. This proves equally unsatisfactory however as a measure to stop Spam mail. Anyone who manages large mailing lists knows that a small percentage of people who subscribe subsequently accuse the sender of spamming them when they receiv
