Domain blocklist check
See whether a domain name is on the lists that spam filters use to judge the links and senders in an email.
Why domains get listed
Spam filters do not only look at the server that sends a message. They pull every domain out of the message too, from the links, the sender address and the reply address, and look each one up on domain blocklists. A single listed link can send an otherwise clean newsletter to the spam folder.
Enter a domain and we check its registered name and, when you enter a subdomain, the exact host as well. We ask Spamhaus DBL, URIBL and the SpamEatingMonkey lists, and when the registry shows it, we tell you how new the domain is.
The domain lists and their codes
| List | Answer | What it means |
|---|---|---|
| Spamhaus DBL | 127.0.1.2 | A domain used in spam |
| Spamhaus DBL | 127.0.1.4, .5, .6 | Phishing, malware or botnet control |
| Spamhaus DBL | 127.0.1.102 to .106 | A real site that was hacked or abused for spam, phishing or malware |
| URIBL | 127.0.0.2 | Black: belongs to spammers |
| URIBL | 127.0.0.4 | Grey: appears in bulk mail, some are false positives |
| URIBL | 127.0.0.8 | Red: young, monitored or hides its details |
| SpamEatingMonkey | 127.0.0.2 | Seen in spam, or only a few days old on the fresh list |
The result decodes these codes into plain words, shows the reason text the list publishes, and links the list's own removal form. A list that is not answering is switched off for a while and shown under Not checked, so it does not look like a clean result.
New domains and abused sites
New domains send most of the spam, so some filters score a domain down for its first days or weeks, whatever it does. The age list marks a domain that was registered very recently. That is not a punishment: it leaves the list by itself, and the best answer is patience and a slow, steady sending pattern.
A listing of the "abused legitimate site" kind means your site was hacked or misused, often through an outdated plugin, a weak password or an open form that sends mail. Fix that first. The list will not remove a site that still sends spam links.
Getting a domain removed
- Clean up the causeRemove hacked pages, update the site software, change passwords and check the mail forms. Look at the pages that carry links to the listed domain.
- Use the list's removal formThe Listings tab links the form of each list that has you. Describe what you fixed in a sentence or two. Do not ask several times in a row, as that slows the review.
- Check that mail authentication passesConfirm SPF and DMARC pass for the domain, so receivers can tell your real mail from forged mail that uses your name.
Questions people ask
What is a domain blocklist?
It is a list of domain names, kept in DNS, that have been seen in spam, phishing or malware. Mail filters extract domains from a message and look them up. Unlike an IP list, it follows the content of the mail, so a clean server can still be penalised for a bad link.
Can my domain be listed if I never sent spam?
Yes. A hacked website, a link in someone else's spam, a shared link shortener or a lookalike of a known bad domain can all lead to a listing. The code tells you which case applies, and the abused legitimate site codes exist for exactly this.
Why was a list refused or not checked?
Some lists block resolvers that ask too often, and they answer with an error code that looks like a listing. We read those codes as a refusal, not as a listing. A list that does not answer our tests is switched off until it does, and the result says so.
Does a young domain age count against me?
For a short while, with some filters. The fresh-domain list is not a spam verdict. Send a small, steady volume to people who expect your mail, and keep authentication passing, and the effect fades as the domain gets older.
What is the difference between URIBL black, grey and red?
Black means the domain belongs to spammers. Grey means it showed up in bulk mail, and may be a legitimate sender that honours opt-outs. Red marks young or monitored domains. Filters usually add points for these instead of rejecting.
Should I check the root domain or the subdomain?
Check the name that appears in your mail. Most lists track the registered domain, so we always check that, and we add the exact host when you type a subdomain, because a few lists record hosts.
Use it from AI, the API or the command line
Every LookupOwl tool is also a free API and an MCP tool, with no key and no account. This one is blacklist_check. Please be kind to the rate limits.
curl "https://lookupowl.com/api/v1/tools/blacklist-checker?q=example.com"claude mcp add --transport http lookupowl https://lookupowl.com/mcp