DNS Blocklists

DNS Blocklists are a common form of network-accessible database used in spam detection. They're also referred to as "DNS Blacklists" and "RBLs". (The latter usage is incorrect for the general case, as "RBL" is a trademark of MAPS, LLC.)

SpamAssassin includes support for many of the bigger DNSBLs, with optimal scores (or at least, optimal as determined by the GeneticAlgorithm).

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Note that SpamAssassin still works very well without using these two services, however.

Live accuracy figures for most of the DNSBLs used in [SpamAssassin], based on the Oct 2003 mail feed for one user, can be found

 \[http://taint.org/2003/11/07/184247a_mail.html

 here\].

Other places to find out about DNS blacklists / blocklists:

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\[http://www.blocklisting.com/faq.html news.admin.net-abuse.blocklisting\] is a newsgroup devoted to discussion of subjects related to the use, administration, and effects of blocklists in ameliorating the problem of unsolicited bulk email and other unwanted or abusive network traffic.  It is also accessible through \[http://groups.google.com/groups?group=news.admin.net-abuse.blocklisting groups.google.com\].

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Comments:

Q: This documentation doesn't seem to cover how to configure dns-blocklists. It says "Support for these is built-in" but I can't believe that all free BL's is called each time a mail is beeing checked. There must be a way to configure which to use.

A: See the Mail::SpamAssassin::Conf documentation page, and the rules file 20_dnsbl_tests.cf , for details and examples of how to add a new DNSBL lookup rule.