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TOOL: BLACKLIST CHECKER

Email Domain Blacklist Checker

Check a domain or IPv4 address against 14 public blocklists before you start sending. One at a time, or up to 100 in a list.

What this checker does

It runs two checks. Ten address blocklists are queried against the IP that sends the domain’s mail, and four domain blocklists are queried against the domain name itself. Each list is reported separately, so a listing can be traced to the operator that published it rather than reduced to a single pass or fail.

The two answer different questions. An address listing says the machine sending your mail has a reputation problem. A domain listing says your name does, and that one follows your mail to every recipient no matter which server relays it.

Given a domain, it checks the address behind the domain’s MX record rather than the website. Blocklists judge the machine that sends mail, and for most domains that is not the server hosting the marketing site. Two unrelated domains on the same web host share one address and would otherwise return the same meaningless verdict.

That also means a domain sending through Google, Microsoft or another shared provider is being checked against an address that carries mail for millions of senders. A clean result there is the provider’s reputation rather than yours, which is why the result says so. On shared infrastructure the domain lists are the half of this check that is actually about you.

Lookups are live. A delisting that has just gone through shows up as soon as the operator's zone reflects it.

Reading the result

Not listed across every list is the expected state for a healthy sending domain. It rules out one cause of poor delivery without proving reputation is good.

Listed on Spamhaus ZEN is the most consequential result here and is worth treating as urgent. It affects acceptance at a large share of receivers immediately.

Listed on one smaller list only is worth investigating but rarely explains a collapse on its own. Look for what triggered it rather than focusing on the listing itself.

Not checked means the list answered with a status code instead of a result. Spamhaus declines queries that arrive through a public resolver, which is a limit of free DNSBL access rather than a finding about the address.

What actually causes listings

Volume ramped too quickly. A new domain sending at full rate before any warmup is the most common cause on cold email infrastructure.

Poor list quality. Scraped or aged lists produce hard bounces and spam trap hits, and traps are exactly how several of these lists build their data.

Complaints. Recipients marking mail as spam feeds reputation systems directly, and enough of it will surface as a listing.

A listing is a symptom. Delisting without changing volume, list hygiene or targeting means doing it again shortly.

Which lists to worry about

Not every listing carries the same weight, and treating them as equal wastes effort on the ones nobody consults.

Spamhaus is the one that matters most on both sides. ZEN for addresses and DBL for domains are consulted by a very large share of receivers, and a listing on either is felt within hours. Treat it as urgent.

SURBL and URIBL are the domain lists most spam filters check against links and sender domains inside a message. A listing here reaches you even when your sending address is spotless.

The smaller address lists - SORBS, PSBL, UCEPROTECT, DroneBL and the rest - have narrower adoption. One of them alone rarely explains a delivery collapse, but several at once is a pattern worth reading as an early warning.

What to do about a domain listing

Find the cause before requesting removal. Domain lists are usually triggered by the domain appearing in mail that recipients reported, by links pointing at a domain already flagged, or by a redirect chain ending somewhere with a bad reputation. Registering a domain that a previous owner burned is a quieter version of the same problem, which is why a listing can appear on a domain that has never sent a message.

Each operator publishes its own removal process. Spamhaus DBL and SURBL both run lookup pages that state the reason for a listing, and that reason is worth reading before filling in anything, because a removal granted without a change is a relisting waiting to happen.

If the domain was burned before you owned it and the sending reputation cannot be recovered, replacing it is cheaper than fighting for it. That is the argument for keeping cold outreach on domains separate from the one your business actually runs on.

How do I check many domains or IPs at once?

Switch to Bulk list and paste up to 100 domains or IPv4 addresses, one per line, or load a text or CSV file and the first column is used. Each entry is checked against the same 14 lists and comes back as a row: verdict, which lists it is on, how many answered and how many did not. Download the table as CSV.

The limit is 100 entries per batch and three batches a minute, the same for a guest and a signed-in user. A list that does not answer is counted rather than hidden, because a clean result across lists that were never asked is not a clean result.

Common questions

Yes. Switch to Bulk list, paste up to 100 domains or IP addresses one per line or load a CSV, and every row comes back with which lists it is on, how many were checked and how many did not answer. Download the table as CSV. The same limit applies whether or not you are signed in.

Ten address lists and four domain lists. The address lists are Spamhaus ZEN, SpamCop, Barracuda, SORBS, PSBL, UCEPROTECT Level 1, Mailspike, Anonmails, DroneBL and s5h. The domain lists are Spamhaus DBL, SURBL, URIBL and NordSpam DBL. Each is reported separately so a listing can be traced to the operator that published it.

An address list records IP addresses that have sent spam, so it judges the machine your mail leaves from. A domain list records domain names found in spam, so it judges your name. If you send through a shared provider, the address belongs to that provider and the domain is the only part of the pair that is yours.

Because it travels. Changing provider gives you a new sending address and a clean address reputation, but the domain in your From header stays the same, and a domain listing follows it. A listed domain is also visible to any receiver checking the links and addresses inside the message, not just the connection it arrived on.

An IP address, always. DNSBLs list addresses rather than names, so entering a domain resolves the address behind its MX record and checks that. The mail host actually checked is shown with the result, because for most domains it is not the same machine that serves the website.

Because blocklists judge the machine that sends mail. A domain’s A record points at whatever hosts its marketing site, and two unrelated domains on the same platform share one address, so checking it returns an identical and meaningless verdict for both. The MX host is where the mail actually comes from.

Only partly. A shared provider’s relay carries mail for millions of senders and its reputation is the provider’s, not yours, so it is almost always clean regardless of how you send. The result says so when a shared host is detected. On shared infrastructure the signals that belong to you are domain reputation, authentication and complaint rate, not the relay’s blocklist status.

Spamhaus refuses queries that arrive through a public DNS resolver and answers with a status code in the 127.255.255.0/24 range rather than a result. That is a condition of free access, not a finding about the address, so it is reported as not checked rather than counted either way. Each Spamhaus row links to their own lookup page with the address or domain filled in, which answers the same question directly. Querying Spamhaus from a service requires their paid Data Query Service.

Fix the cause first, then request removal through the list operator. Delisting without fixing the underlying behaviour leads straight back to a relisting, usually faster and for longer. Most operators publish a removal form; some delist automatically once the signal stops.

It varies by operator, from automatic expiry within days to manual review. What matters more is that the sending pattern that caused it has actually changed, because a relisting is quicker to trigger than the first one.

Public blacklists are only one input. Receivers run their own internal reputation systems that are far more influential and are not published anywhere. A clean blacklist result rules out one cause; it does not confirm good reputation.

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