The Internet Research Task Force has published informational RFC 6471 on DNSBL operational practices. The acronym DNSBL stands for ‘DNS-based list’, which is more apt than ‘DNS blacklist’ as the DNSBL format can also be used to publish whitelists.
One of the recommendations in the RFC, which is authored by Chris Lewis of Nortel and Matt Sergeant of Symantec, states that a DNSBL should, as a minimum, provide a web page that has a removal request function. At present, one widely known DNSBL states that it does not accept removal requests. This has led to such requests instead being posted to the Usenet newsgroup news.admin.net-abuse.email. If removals are not automated, it is particularly important that the DNSBL have multiple administrators who can cover for each other’s absence. – The RFC also requires that negative-connotation DNSBLs not charge fees (or require donations) for delisting or faster handling.
When the list is discontinued, it must be shut down gracefully, not e.g. by listing the entire Internet (as has been done in the hope of encouraging mail server operators to stop querying the list). A recommended way to shut down operations is to delegate the sub-domain name of each list zone (not the base domain of the list provider) using an NS record pointing to a test address (i.e. to an IP address in one of the class C networks 192.0.2, 198.51.100 and 203.0.113). To avoid abuse of the list’s base domain name, it should be registered indefinitely, i.e. not allowed to lapse.
RFC 6471 is available at http://www.rfc-editor.org/rfc/rfc6471.txt.
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