Email blacklist checker

See whether a domain, or the servers behind it, appear on well-known DNS blacklists.

What is an email blacklist?

A DNS blacklist (DNSBL) is a list of IP addresses or domain names that a maintainer has linked to spam, malware or abuse. Receiving servers query these lists over DNS while a message is arriving, and may reject it, filter it or raise its spam score when the sender is listed. Different lists have different criteria and different consequences, so a listing on one is not equal to a listing on another.

How this checker works

Everything happens in your browser through Google Public DNS. The tool resolves the A record and up to three MX hosts for your domain, takes up to six IPv4 addresses, reverses the octets of each (for example 203.0.113.7 becomes 7.113.0.203) and queries that name under each list: Spamhaus ZEN, SpamCop, Barracuda, SORBS and PSBL. It also queries the domain itself against the Spamhaus Domain Block List and SURBL. A return code in the 127.0.0.0/8 range means listed, and an NXDOMAIN answer means not listed.

Why some results say “could not check”

Several lists restrict who may query them. Spamhaus, in particular, refuses queries that come through large public resolvers and answers with codes in 127.255.255.x instead of a real result. Barracuda expects the querying resolver to be registered with it. Other lists may time out, change how they operate over time, or stop answering. This tool never reports those cases as clean. If you see “could not check” for a list that matters to you, query it from your own resolver or use that list’s own lookup page.

What a listing means, and what to do

The return code identifies the reason and the list’s website explains it and the delisting process. Common causes are a compromised account, a shared IP with a noisy neighbour, a sending server that is not fully authenticated, or a very new IP with no history. Fix the cause first, because removal requests tend to fail or be undone if the problem remains. Clean addresses and authenticated mail help: verify the list you send to, and check your SPF, DKIM and DMARC records.

Limits to keep in mind

This is a snapshot of a handful of lists. Passing them does not guarantee inbox placement, because mailbox providers also rely on their own reputation systems. Being listed does not always mean your mail is blocked either. The sending IP that matters is the one that actually delivers your mail, which may belong to an email service provider rather than to the addresses in your domain’s A or MX records. The sending setup guide covers preparing a domain properly.