Short for DNS Based List, DNS Blacklist, or DNS Blocklist.
A published list of IP addresses that can be queried through the Internet. DNSBLs are used to publish IP addresses associated with e-mail spam and spamming. Most mail servers can be configured to reject messages from addresses on a DNSBL. An address found in a DNSBL may be directly associated with spam, or may have made the list due to Web server vulnerabilities that can be used by spammers. There are many DNSBLs available, each published and maintained by different individuals and organizations.
See also Realtime Blackhole List.