A DNS blocklist is a zone that answers a DNS query for a reversed IP address. If the address is listed, the zone returns a code in 127.0.0.0/8 and usually a TXT record explaining why. Receiving mail servers query these zones during the SMTP conversation.

How do I get delisted from a blocklist?

Fix the cause first, then use that list's own removal form. Spamhaus and Barracuda both self-remove once the traffic stops. Delisting while the problem continues gets you relisted within days, and some lists apply a longer hold each time.

Does being on a blocklist mean my mail bounces?

It depends on which list and which receiver. Spamhaus ZEN is consulted almost everywhere and a listing there is serious. Plenty of smaller lists are queried by almost nobody, which is why a checker that reports hundreds of zones produces more alarm than information.

Blacklist checker

Check a sending IP or a domain against the public blocklists that receiving servers really query, with the reason text each list publishes.

Enter the IP you send from, or a domain, and we will query the public blocklists that receivers actually consult.

What this cannot tell you

Clear here is not the same as trusted. Gmail, Microsoft and Yahoo each keep an internal reputation score for your sending IP and domain, and none of them publish it. Mail can land in spam at all three while every public list says you are fine.

We query a short list of zones on purpose. Checkers that report two hundred lists include zones nobody consults, zones that have been abandoned for years, and a few that list entire countries. A red row from a list no receiver queries is noise dressed as an alert.

A listing does not always name the machine at fault. Shared hosting and cloud ranges get listed as blocks, so your address can be listed for something a neighbor did. The reason text is usually the fastest way to tell which situation you are in.

Spamhaus is likely to show as not reached here, and that is by their design rather than a fault at our end. They refuse queries arriving through shared resolvers and answer with an error code instead of a verdict. We report that as no answer, because treating their error as a listing would mark every domain on the internet as blocked. Their own lookup page at check.spamhaus.org gives you the real answer for that one zone.

None of this speaks to your list quality, which is usually the underlying cause. Mailing addresses that do not exist is what gets a sender listed in the first place, and that is what spam traps are built to catch.

IP lists and domain lists answer different questions

An IP blocklist is about the machine that opened the connection. Most of them list for volume from an address with no history, for output from a compromised host, or for hits on addresses that only exist to catch senders.

A domain blocklist is about names found inside the message: the sending domain, the link domains, the tracking domain. This catches the sender who keeps rotating IP addresses while using the same domain in every campaign.

Both matter and they fail differently. Moving to a fresh IP escapes an IP listing and does nothing for a domain listing. Buying a new domain does the reverse. Neither is a fix if the sending behavior stays the same, and each rotation makes the next listing arrive faster.

List	Checks	How much receivers use it
Spamhaus ZEN	IP addresses	Consulted very widely. A listing here is serious
Spamhaus DBL	Domains	Widely used for domains found in message bodies
SpamCop	IP addresses	Fed by user reports, and expires listings automatically
Barracuda	IP addresses	Used by Barracuda appliances, common in mid-sized firms

Zone behavior as documented by each operator, checked September 2026. SORBS is absent on purpose: it was shut down in June 2024 and its zone no longer resolves, so a tool that still queries it is reporting nothing.

What to do about a listing

Read the reason before you touch a removal form. Most lists publish a TXT record with a short explanation and a link, and that text usually names the behavior: a spam trap hit, a volume spike, output from a compromised account.

Then find the cause. A sudden listing after a campaign points at the list you mailed. A listing on an IP you share with other tenants points at your host. A listing that keeps coming back after each removal means the underlying traffic never stopped.

Only then request delisting. Spamhaus and several others remove automatically once the traffic stops, so patience costs nothing. Repeatedly requesting removal while the cause continues is the reliable way to earn a longer hold next time.

Questions people ask

I send through an ESP. Whose IP should I check?

The one in the Received headers of a message you actually sent, which the header analyzer will show you. On a shared pool it belongs to the provider, and a listing there is their problem to fix rather than yours.

How did I get listed when I only mail people who signed up?

Recycled traps are the usual answer: an address that was real, was abandoned, and was later turned into a trap by the provider. Old addresses on a list nobody has cleaned for two years are exactly how this happens.

Is a listing on one small list worth worrying about?

Usually not on its own. Check whether the receivers you actually mail consult it. Listings on several lists at once are the signal, because that pattern means the behavior was noticed independently.

Can a competitor get me listed?

Not easily. Listings come from observed traffic and trap hits rather than complaints alone, so manufacturing one against a sender who is behaving normally takes more effort than it is worth.

Other tools

Most listings start with a list nobody cleaned

Dead addresses and recycled traps are what put a sender on these zones. Verification removes the first and reduces the odds on the second, without claiming to detect what cannot be detected.

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