Is your domain on
a blacklist?
One pass across 17 blocklists, Spamhaus and Barracuda and SpamCop among them, plus Google Safe Browsing. Works with a domain or an IP, and we find your mail server automatically, because that’s where listings actually hide.
Which blacklist is your problem?
“Blacklisted” means four different things depending on who holds the list. One check covers the public ones — and tells you how to read the private ones.
Mail blocklists
Spamhaus, Barracuda, SpamCop — DNSBLs that mail servers query live, mid-delivery. A listed sending IP means spam folders and 550 rejects.
the spam-folder oneDomain blocklists
DBL and SURBL list the name, not the IP. A listed domain poisons any email that so much as links to it — whoever sends it.
the poisoned-link oneGoogle Safe Browsing
The browser blacklist: Chrome’s full-screen red warning, plus a “this site may harm your computer” flag in Search results.
the red-screen onePrivate reputation
Gmail, Microsoft and Apple keep internal lists nobody can query. You read them through bounce codes — we show you what to look for.
the silent oneA blacklist is just a DNS zone
There’s no registry office and no phone call. A DNS blocklist is a DNS server that answers questions about IPs and names. That’s why checking one is instant, and why this page can run 23 of these queries in one pass:
- To ask Spamhaus about 198.51.100.25, reverse the octets and resolve 25.100.51.198.zen.spamhaus.org. An answer means listed; NXDOMAIN means clean.
- The answer is a code: 127.0.0.3 says “compromised sender”, 127.0.0.10 says “residential IP, policy only”. Same query — very different advice.
- Domain lists work the same way, un-reversed: caldmont.com.dbl.spamhaus.org.
- It’s plain, unauthenticated DNS — cheap enough that mail servers check every incoming connection this way, in real time.
Return codes, decoded
what the DNS answer meansWho actually uses each list
Panic is optional. A Spamhaus listing is a today-problem; a UCEPROTECT listing is usually a nothing-problem. Weight every listing by who consults the list.
The one that matters most. Consulted by mail servers worldwide and weighed by the big providers. A listing here hits delivery within hours.
Ships inside Barracuda firewalls and appliances, common in front of corporate mail. A listing means hard 550 rejects at thousands of companies.
Fed by user spam reports and spam traps. Real, but self-healing: listings expire on their own within 24–48 hours once the reports stop.
Smaller lists with modest reach. Worth clearing for hygiene, but rarely the reason your mail is bouncing — check the big two first.
Lists whole networks: Level 3 flags your host’s entire AS because of other customers. Almost nobody filters on it — and “express delisting” costs money by design.
Private reputation systems — not queryable by anyone. You read them via bounce codes (Gmail 5.7.28, Microsoft 5.7.606) and their postmaster dashboards.
Check any blacklist with dig alone.
Every DNSBL answers plain DNS queries. This page runs 23 of them in one pass and decodes the return codes for you.
Common questions
Type either above. For a domain we resolve the website's IP and find the mail server via its MX records. Then we check the domain name, both IPs and Google Safe Browsing: 25 queries in one pass. It's free and needs no sign-up. We query from a clean resolver, so public-resolver false positives (that 127.255.255.254 answer) never sneak in.
Almost certainly not. Home and office connections sit on the Spamhaus PBL and similar “dynamic IP” lists by design. That is policy, not an accusation: residential IPs aren't supposed to run mail servers, so receivers ignore mail sent from them directly. It only matters if you actually operate a mail server on that IP. Your normal email goes out through your provider's servers, and that is whose reputation counts.
Blacklists are one input among many. The usual suspects, in order: missing or broken authentication (SPF, DKIM and DMARC are all DNS records), a weak domain reputation, spammy content patterns, and sudden volume spikes. For your actual standing with Gmail, use Google Postmaster Tools. It is free, and it shows the reputation Google itself has assigned your domain.
The classics: a compromised contact form or WordPress plugin quietly relaying spam, a leaked SMTP password, malware on the server, or a purchased address list that hit spam traps. Sometimes it is just a bad neighbor on a shared hosting IP. Either way the fix starts with finding the source, not with the removal form.
Fix the cause first, or you'll be relisted within 48 hours. Then: Spamhaus has free self-service removal, Barracuda a free request form, and SpamCop expires on its own in 24–48 hours. And one rule holds throughout: never pay for delisting. Every list that matters removes you free; paid “express delisting” is a business model, not a service.
Google Safe Browsing — the database behind Chrome's full-screen red warning and the “this site may harm your computer” tag in Search. It flags malware, phishing and deceptive pages, and it's included in every check this page runs. If you're flagged: Google Search Console shows exactly which URLs tripped it, and you request a review there after cleaning up.
Because they're private — no public query interface exists, for anyone. You learn you're on them from bounce codes: 5.7.606 from Microsoft, 5.7.28 from Gmail. Microsoft has a sender-delisting portal and SNDS for IP standing; Gmail has Postmaster Tools. We check everything that's publicly checkable — and tell you which bounces to read for the rest.
Free tools are just the start.
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