Blacklist Check

About the blacklist check

DNS-based blacklists (DNSBLs) are lists of IP addresses reported as sources of spam, malware or abuse, published in a form mail servers can query as part of deciding whether to accept an incoming message. Being listed on even one widely-consulted blacklist can cause a significant share of your outgoing mail to be silently dropped or routed to spam folders. This tool resolves a domain's mail server addresses, or takes a single IP you provide, queries each list, and reports which ones list it along with the return code and, where the list publishes one, the stated reason.

We are explicit about what this check does not cover, because a clean result from a narrow set of lists reads exactly like a clean result from a broad one. Spamhaus is the list most mail providers actually consult, and we do not query it: its free public mirror is licensed for non-commercial use only, as are SURBL, URIBL and Google Safe Browsing, and dotvitals is a commercial site. Querying them would breach those terms, and the compliant paid feeds are not something we have bought. Every run of this check says so, and names both the lists it asked and the lists it did not. You can check Spamhaus yourself for free at check.spamhaus.org, and you should, because this check alone does not tell you whether you are listed there.

Lists also differ enormously in weight, and a listing is not automatically a problem. Some of the lists queried here are consulted by a great many mail servers; others are aggressive by policy and list entire network ranges to pressure the network operator rather than because of anything the individual address did. Read a listing as a lead to investigate — check what the list itself says about why it lists, and whether the provider whose delivery you are worried about actually consults it — rather than as a verdict.

Listings usually happen for a concrete reason: a compromised server sending spam, a shared IP previously used by someone else for abuse, misconfigured mail relaying, or complaint rates that crossed a provider's threshold. Most reputable lists publish a delisting process once the underlying cause is fixed, and delisting is rarely automatic even after the problem is resolved. Because many blacklists key off the sending IP rather than the domain, a domain switching mail providers, or moving to a new server on a previously-abused IP range, can inherit a listing it had no part in causing, which is worth checking before troubleshooting deliverability from other angles.

A list that does not answer is reported as not having answered. A timeout, a server failure, a refusal because the querying resolver is not registered with that list, or an answer outside the range the list documents are all treated as an unknown result for that list, never as a clean one. This matters more than it sounds: several lists refuse queries from large public resolvers by policy, and a tool that silently converts a refusal into a green tick is the reason people believe they are not listed when they are.

Running this check periodically, not just when deliverability problems are already reported by users, catches a listing while it is still small and easy to remediate, rather than after it has already caused a noticeable share of legitimate mail to go missing. A quick recurring check costs little and catches a listing while its cause is still fresh and easy to trace, well before it has had time to accumulate into a noticeable, harder-to-diagnose drop in inbox placement.

Common questions

What is a DNSBL?

A DNS-based blacklist: a published list of IP addresses associated with spam or abuse, structured so mail servers can query it automatically during delivery decisions.

I'm listed, what do I do?

Fix the underlying cause, whether that is a compromised server, an open relay or high complaint rates, then follow the specific list's delisting process; most require a manual request and are not automatic.

Do you check Spamhaus?

No. Spamhaus, SURBL, URIBL and Google Safe Browsing license their free access for non-commercial use only, and this is a commercial site, so querying them would breach those terms. Every result says so and names what was and was not checked. Check Spamhaus yourself, free, at check.spamhaus.org.

Does being on one blacklist affect all my mail?

It depends entirely on the list. Some are consulted by a great many mail servers; others list whole network ranges as a pressure tactic against the network operator and are consulted by very few. Find out who actually uses the list before deciding how much work a delisting is worth.

Can a new server inherit an old blacklisting?

Yes. Many blacklists track IP addresses, not domains, so an IP previously used by someone else for spam can still be listed when you start using it, even though you did nothing wrong.