Glossary: DNSBL (DNS Blacklist)
A DNSBL is a database of IP addresses known to send spam or engage in malicious activity.
How DNSBLs Work
DNSBLs use the DNS system to maintain lists of IP addresses. When a mail server receives a connection, it queries the DNSBL by reversing the IP and appending it to the blacklist domain. A positive response indicates the IP is listed.
Types of Blacklists
- Spam blacklists: IPs known to send spam
- Open relay lists: Improperly configured mail servers
- Malware lists: IPs hosting or spreading malware
- Policy lists: IPs violating specific policies
- Reputation lists: Scored based on behavior
Getting Delisted
To remove an IP from a blacklist:
- Identify and fix the problem
- Check each blacklist's removal procedure
- Submit delisting requests with evidence
- Monitor to prevent re-listing