• A service for the operation of mail servers, performing checks via Domain Name System (DNS) queries whether a sending host’s IP address is blacklisted for email spam. 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. Since the creation of the first DNSBL in 1998, DNSBLs have frequently been controversial, being objected to as a form of censorship. ← Wikipedia

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