What are Real-time Blackhole Lists (RBL)?
Which checks and input types are supported?
Use an IP address or domain, not an email address. An HTTP or HTTPS URL is also accepted as a convenience: only its hostname is checked, not the page or URL path. Domain results separate domain-zone checks from checks of selected resolved addresses; they do not discover or test every mail server for that domain. Provider coverage varies by address family. Unknown IPv6 capability is reported as unavailable rather than assumed supported.
How should I interpret the result states?
Listed means the DNS query returned an A-record response; inspect the displayed response code and confirm its meaning with the operator, because provider access or policy responses can require interpretation. Clean means no listing A record was observed in a successful DNS response, not proof of good reputation. Checked counts queries attempted, not necessarily successful checks. Unsupported means the address family is explicitly unsupported. Unavailable includes unknown IPv6 support, DNS failures and exhausted query budgets; Error includes DNS REFUSED. Neither unavailable nor error means not listed.
What should I do after a listing?
Confirm the listing and response code with the blacklist operator. Investigate mail logs, compromised accounts, open relays, malware and shared or dynamic address policies as relevant. Fix the underlying issue, then follow that operator’s removal procedure; this tool cannot remove listings. Some lists expire entries, while others require a request or other conditions.
Does a clean result establish inbox delivery?
No. Results cover only the configured zones and selected addresses from this resolver’s view. Receiving providers apply additional reputation, authentication and content rules. Update schedules and removal procedures depend on each blacklist operator; there is no universal removal deadline. Example (illustrative, not a live result): an address with no observed listing can still have mail rejected for failed authentication.
For a message-level authentication and SpamAssassin report, send a test message using the Mail Tester. To investigate published sender policy separately, use the SPF checker. Neither check guarantees inbox placement.