IP Blacklist Check

Enter an IPv4 address to see if it appears on a selection of common DNS blacklists (DNSBL). This is especially useful when troubleshooting bounced or rejected email.

Only IPv4 addresses are supported for blacklist checks.

What Are DNS Blacklists?

DNS-based blacklists (DNSBL) are databases that track IP addresses known to send spam, malware, or abusive traffic. Mail servers query these lists before accepting messages, and may reject or flag email if the sending IP appears on one or more blacklists.

Being listed does not always mean intentional abuse; misconfigured servers, compromised systems, or shared hosting environments can also trigger blacklisting.

How to Use the Blacklist Check

  1. Identify the public IP address used to send email.
  2. Enter the IP address into the form above.
  3. Review which DNSBL providers, if any, report the address as listed.
  4. Visit the provider's website for details and, if needed, follow their delisting procedure.

Important Considerations

  • Different mail providers rely on different blacklists; appearing on one list does not guarantee delivery problems everywhere.
  • Some lists are very aggressive and may list entire ranges or shared hosting providers.
  • This tool checks a limited set of public DNSBL providers and does not cover every possible blacklist.
  • Always consult your email service provider or mail server logs for the definitive reason a message was rejected.