Domain Name System blocklist

A Domain Name System blocklist, Domain Name System-based blackhole list, Domain Name System blacklist (DNSBL) or real-time blackhole list (RBL) is a service for operation of mail servers to perform a check via a Domain Name System (DNS) query whether a sending host's IP address is blacklisted for email spam.^[1] Most mail server software can be configured to check such lists, typically rejecting or flagging messages from such sites.

A DNSBL is a software mechanism, rather than a specific list or policy. Dozens of DNSBLs exist.^[2] They use a wide array of criteria for listing and delisting addresses. These may include listing the addresses of zombie computers or other machines being used to send spam, Internet service providers (ISPs) who willingly host spammers, or those which have sent spam to a honeypot system.

Since the creation of the first DNSBL in 1998, the operation and policies of these lists have frequently been controversial,^[3]^[4] both in Internet advocacy circles and occasionally in lawsuits. Many email systems operators and users^[5] consider DNSBLs a valuable tool to share information about sources of spam, but others including some prominent Internet activists have objected to them as a form of censorship.^[6]^[7]^[8]^[9] In addition, a small number of DNSBL operators have been the target of lawsuits filed by spammers seeking to have the lists shut down.^[10]

^ "What is a DNSBL". DNSBL.info. Retrieved 21 June 2020.
^ "DNS & RHS blackhole lists". Archived from the original on 2013-03-21. Retrieved 2013-03-26.
^ Lewis, Chris; Sergeant, Matt. Overview of best email DNS-based list (DNSBL) operational practices. doi:10.17487/RFC6471. RFC 6471. Retrieved 2020-05-25.
^ "RBLMon.com: What are RBLs and How do they Work?". Archived from the original on 2017-09-04. Retrieved 2013-03-26.
^ "Revealing Botnet Membership Using DNSBL Counter-Intelligence" (PDF). Retrieved 2013-03-26.
^ "RBL Criticism". 11 February 2008. Retrieved 2013-03-26.
^ "Electronic Frontier Foundation, EFFector, Vol. 14, No. 31, Oct. 16, 2001". 12 January 2012. Retrieved 2013-03-26.
^ "Verio gags EFF founder over spam". The Register. Retrieved 2013-03-26.
^ "Choosing Spam over Censorship". Archived from the original on 2003-04-21. Retrieved 2013-03-26.
^ "EMarketersAmerica.org sues anti-spam groups". Retrieved 2013-03-26.

[1] "What is a DNSBL". DNSBL.info. Retrieved 21 June 2020.

[2] "DNS & RHS blackhole lists". Archived from the original on 2013-03-21. Retrieved 2013-03-26.

[3] Lewis, Chris; Sergeant, Matt. Overview of best email DNS-based list (DNSBL) operational practices. doi:10.17487/RFC6471. RFC 6471. Retrieved 2020-05-25.

[4] "RBLMon.com: What are RBLs and How do they Work?". Archived from the original on 2017-09-04. Retrieved 2013-03-26.

[5] "Revealing Botnet Membership Using DNSBL Counter-Intelligence" (PDF). Retrieved 2013-03-26.

[6] "RBL Criticism". 11 February 2008. Retrieved 2013-03-26.

[EFF-Effector-7] "Electronic Frontier Foundation, EFFector, Vol. 14, No. 31, Oct. 16, 2001". 12 January 2012. Retrieved 2013-03-26.

[8] "Verio gags EFF founder over spam". The Register. Retrieved 2013-03-26.

[9] "Choosing Spam over Censorship". Archived from the original on 2003-04-21. Retrieved 2013-03-26.

[10] "EMarketersAmerica.org sues anti-spam groups". Retrieved 2013-03-26.

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