Free blacklist checker
Is your sending IP on a spam blacklist?
We find your mail servers, then check each one against 5 major blacklists used by real inbox providers. A listing here is often the actual reason mail is landing in spam.
How this check works
We look up your domain's MX records, resolve each mail server hostname to its IP addresses, and query five DNSBLs for each IP. A blacklist "listing" is just a special DNS answer in the 127.0.0.0/8 range at a specially-formatted lookup address — no answer means clean, a 127.x answer means listed.
If most of your mail goes through a large shared provider (Google Workspace, Microsoft 365), a listing is rare and usually temporary — shared IPs get delisted quickly because providers actively manage their reputation. A listing is more common, and more worth investigating, on a dedicated or self-managed mail server.
Common questions
What is an email blacklist (DNSBL)?+
A DNSBL (DNS-based Blacklist) is a public list of IP addresses that have been reported for sending spam or other abusive mail. Many inbox providers check incoming mail against these lists before deciding whether to deliver it, send it to spam, or reject it outright.
Which blacklists does this tool check?+
Barracuda Reputation Block List, SpamCop, PSBL, UCEPROTECT Level 1, and blocklist.de. We intentionally leave out a couple of well-known lists (including Spamhaus) that actively detect shared public DNS resolvers and return a deliberately fake result to them instead of real data — checking those reliably requires infrastructure this free, in-browser tool doesn't have, and we'd rather show you five trustworthy results than six unreliable ones.
I'm listed — what do I actually do about it?+
Each blacklist has its own delisting process, usually a form on their website, and most require you to first fix whatever caused the listing (an open relay, a compromised account, a spam complaint spike). Search "[blacklist name] delisting" for the specific provider you're listed on — the fix is almost always on their side, not something DNS changes can undo.
Why does this check my mail server's IP and not my domain?+
Blacklists track IP addresses, not domain names — a spammer's IP gets listed regardless of which domain they claim to be sending from. We resolve your domain's MX records to find the actual IP addresses your mail flows through, then check those.
I switched email providers recently. Could an old IP still cause problems?+
If your MX records still point at old infrastructure, yes — this check will catch that automatically, since it checks whatever IPs your domain's current MX records resolve to. If you've fully migrated, this becomes a clean read on your current provider's shared IP reputation.
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