Is your domain on a spam blocklist?

Published: 2026-08-12

A domain lands on a blocklist and nothing announces it. Letters simply stop arriving: no bounce you would notice, no warning in any panel — the receiving side quietly drops them. If sign-up codes stopped coming, or a form keeps saying “this address cannot be used”, this page is where to start.

Two things happen below. First, the checks that can honestly run in your browser — whether the domain exists, where its mail goes, and whether the three records that decide deliverability are in place. Second, one-click lookups in the big blocklists themselves, opened directly from your browser.

Check a domain

Why the blocklists are not queried on this page

Every “is it listed?” service works the same way underneath: it asks DNS for a specially built name. To ask Spamhaus about example.com you look up the A record of example.com.dbl.spamhaus.org. An answer means listed; no answer means not listed. Simple — and impossible to do from a web page.

A browser cannot send a raw DNS query at all. The only way is DNS-over-HTTPS, which means going through a big public resolver — Google or Cloudflare. And that is exactly what the blocklists refuse to serve:

The other option — querying from our own server — is worse. Free blocklist access is metered per source address, and a server that answers thousands of visitors burns through that budget in an afternoon. After that the address is refused service and the checker returns nonsense for everyone. That is precisely the failure this page is built to avoid, so the lookups are handed to your browser instead.

What the return codes mean

If you ever run a lookup yourself, the answer is an IP in the 127.0.0.0/8 range, and the last number is the actual verdict:

127.0.1.2

spam domain — the classic DBL listing

127.0.1.4

phishing domain

127.0.1.5

malware domain

127.0.1.6

botnet command-and-control domain

127.0.1.102

abused legit domain — someone else's spam runs through it

127.255.255.252

a malformed query, not a verdict

127.255.255.254

you queried through a public resolver — refused

127.255.255.255

too many queries from your address

The last three are not results about your domain. A tool that shows them as “listed” is simply reading its own error message.

Domain lists and IP lists are different things

Two separate questions get mixed up constantly, and the answers have different fixes:

If you use this service with your own domain, the sending side barely concerns you: you only receive. What matters is the receiving setup below — and that is checkable from the browser.

Listed — what now?

• Find out why before asking to be removed. Every list shows a reason. Delisting a domain that still hosts the problem gets it listed again within days, and repeat offenders are treated far more harshly.
• Fix the cause. Usually a hacked site sending mail, an open contact form, or a forgotten subdomain pointing at someone else's server.
• Then request removal. Spamhaus removal is free and usually automatic within hours once the reason is gone. Never pay anyone who offers “guaranteed express delisting” — that service does not exist.
• Newly registered domains are treated with suspicion by default. That is not a listing and there is nothing to remove; it fades as the domain accumulates normal history.

Related pages

• Check your domain — did the MX record work? — whether mail for a domain reaches us and whether you can already pick it in the drop-down.
• How to add an MX record — where the DNS panel hides at each registrar and exactly what to type.
• Use your own domain here — the whole setup, start to finish.
• A confirmation code isn't arriving — when the problem is the sender's side rather than your domain.

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