DNSWL

DNSWL (DNS-based whitelist) is both a generic term and a specific list. The specific list DNSWL.org, lists over 50,000 legitimate SMTP senders.^[1]

Natural language understanding is not a mature field. Common computer processes used for spam filtering apply heuristics to avoid presenting too many useless messages to email recipients. This has the severe impact of reducing SMTP reliability^[2] by creating false positives; i.e., silently dropping legitimate messages. Whitelists tackle the task of vouching for a sender, which implies identifying an accountable party that the sender belongs to.

For IPv6, blacklisting is not a realistic option, because of the greatly increased addresses. So whitelisting can be used to reduce a huge address space to a set of manageable size: first build a global whitelist of IPv6 registered senders, and second blacklist within that. By accepting all authentic sender registration request, it is at least possible to eliminate spambots.^[3]

DNSWL.org was founded on 1 November 2006 by Matthias Leisi.^[4] Legitimate senders can register for free. Most DNS servers are sponsored by various organizations worldwide.^[5]

DNSWL.org lists IP addresses, but also holds domain names, category, and email contact addresses. Each IP address is given a "trustworthiness" level; applications (e.g., SpamAssassin) typically decrease the "spamminess" score of a message by a value proportional to that level.

• Automated whitelist
• Vouch by Reference
• DNSBL black list

• DNS Whitelist – Protect against false positives
• IPv6 Mailserver Whitelist