---
title: "Email Blacklist Checker: Domain & IP Check | Prosyo"
description: "Free email blacklist checker: test a domain and its mail server IPs against widely used DNS blocklists, with clear results and removal steps."
url: "https://prosyo.com/tools/blacklist-checker/"
image: "https://prosyo.com/wp-content/uploads/2026/10/cropped-Prosyo-Icon-Transparent-1.png"
language: "en"
---

Free Tools

# Email Blacklist Checker

Check a domain or IP against widely used DNS blocklists, including the mail servers behind a domain.

Email Blacklist Checker Instant · free

## What is an email blacklist checker?

An email blacklist checker tells you whether a domain or IP address appears on DNS-based blocklists (DNSBLs): public lists of addresses and domains associated with spam, malware or abuse. Many mail servers query these lists for every incoming message. If your sending IP or domain is listed, your email can be rejected outright, or quietly routed to spam, no matter how good the copy is.

This free blacklist checker accepts a **domain** or an **IPv4 address**. For a domain, it checks the domain itself on domain-based lists and then finds the domain’s mail servers through its MX records and checks their IP addresses on IP-based lists. For an IP, it checks the IP directly. Results show each list, what was checked, and whether it is listed, clean, or could not be checked from a public resolver.

## How to use the blacklist checker

1. **Enter your sending domain** (for example `yourcompany.com`) or the IP address of a mail server.
2. **Press “Check blacklists”.** The tool runs dozens of DNS queries in parallel; results usually arrive in a few seconds.
3. **Read the summary**: how many lists you appear on, out of how many could be checked.
4. **Look at each listed row**, then follow the removal steps below.

## Which lists are checked

| List | Type | What it tracks |
| --- | --- | --- |
| Spamhaus ZEN | IP | Spam sources, hijacked and compromised hosts, and IPs that should not send mail directly. The most widely used IP list. |
| Spamhaus DBL | Domain | Domains found in spam messages, phishing and malware. |
| SpamCop | IP | IPs reported by recipients for sending spam. Listings expire automatically when reports stop. |
| SURBL | Domain | Domains that appear in unsolicited messages, especially as links. |
| URIBL | Domain | Domains found in spam message bodies. |
| PSBL | IP | IPs that send to spam traps. |
| UCEPROTECT Level 1 | IP | Individual IPs seen sending to its traps. |
| Mailspike | IP | IP reputation based on observed mail traffic. |
| NiX Spam | IP | IPs sending to German spam traps. |
| DroneBL | IP | IPs running open proxies, botnets and other abusable services. |
| S5H | IP | IPs seen sending spam to its traps. |

### Why some rows say “not checkable”

Spamhaus and URIBL do not answer queries that come through large public DNS resolvers such as Cloudflare’s or Google’s, which is what a browser-based tool must use. Instead of a real answer, they return a special code meaning “query refused”. We show those rows as not checkable rather than pretending you are clean. To check Spamhaus directly, use the lookup on Spamhaus’s own website.

## What a listing means, and what it does not

Lists differ hugely in influence. A listing on Spamhaus, for example, can cause rejections at a large share of business mail servers. A listing on a small or aggressive list may affect almost nobody. Before panicking, check:

- **Which list it is.** Major lists matter; minor ones may not.
- **Whether the listed IP is yours alone.** If you send through Google Workspace or Microsoft 365, the mail server IPs belong to them and are shared by millions of senders; they are rarely listed and delisted quickly when they are. If you send through a shared IP at a small host, a neighbour’s spam can list it.
- **Whether it is the domain or the IP.** A domain listing follows you to any server you send from; an IP listing affects only mail from that address.

## Why domains and IPs get blacklisted

- **Hitting spam traps.** Lists seed addresses that were never used, or that were abandoned years ago. Scraped, bought or very old lists contain them.
- **High complaint rates.** Recipients marking messages as spam, particularly on lists that rely on reports.
- **Sudden volume spikes** from a new or quiet domain.
- **A compromised account or server** sending spam you did not write: a hacked mailbox, a vulnerable contact form, a malware-infected computer on the office network.
- **Bad neighbours** on a shared IP address.
- **Your domain appearing in someone else’s spam**, which can put it on domain lists.

## How to get removed from a blacklist

1. **Find and fix the cause first.** If you request removal without fixing anything, you will be listed again, and repeat listings take longer to clear. Change passwords, check sent folders for messages you did not send, pause campaigns, and clean your list.
2. **Read the listing details** on the list’s own website. Most have a lookup page explaining why and when the address was listed.
3. **Request removal** using the list’s delisting form, where one exists. Many lists, including SpamCop, delist automatically once the problem stops, typically within a day or so.
4. **Avoid paid “express delisting”** from small lists. Reputable lists do not charge for removal.
5. **Recheck here** after the stated delisting time.
6. **Watch for a week.** Keep volume low and lists clean while reputation recovers.

## Staying off blacklists when you send cold email

- **Verify every list before sending.** Remove invalid, disposable and role-based addresses with the [Email Verifier](https://prosyo.com/tools/email-verifier/). Never send to bought or scraped lists without checking them.
- **Keep bounce rates low.** A common working target is under 2%. High bounce rates are the clearest sign of a dirty list, and dirty lists contain traps.
- **Send modest volumes per mailbox** and ramp new inboxes gradually with the [Warm-up Planner](https://prosyo.com/tools/email-warmup-planner/).
- **Use secondary domains for outreach**, so a problem never touches the domain your customers and invoices depend on.
- **Make it easy to say no.** A simple “not relevant? just say so and I will not follow up” reduces spam complaints.
- **Stop on reply** and never email people who asked you not to.
- **Authenticate everything.** SPF, DKIM and DMARC will not keep you off lists by themselves, but unauthenticated mail is treated more harshly. Check them with the [Domain Health Checker](https://prosyo.com/tools/domain-health-checker/).

## Signs your mail is being blocked

You do not always need to run a check to suspect a listing. Bounce messages usually say so directly. Typical rejection texts look like these:

| Bounce text (examples) | Likely meaning |
| --- | --- |
| `554 5.7.1 Service unavailable; Client host [203.0.113.10] blocked using zen.spamhaus.org` | The sending IP is on Spamhaus ZEN. |
| `550 5.7.1 Message rejected due to content restrictions (URIBL/DBL)` | A domain in the message, often a link or your From domain, is on a domain list. |
| `550 5.7.350 Remote server returned message detected as spam` | Microsoft rejected the message as spam; reputation or content, not necessarily a blocklist. |
| `421 4.7.0 Try again later, closing connection` | Temporary throttling: the receiver is rate-limiting you. Slow down. |
| `550 5.7.26 Unauthenticated email is not accepted` | An authentication failure (SPF, DKIM or DMARC), not a blocklist. Check with the [Domain Health Checker](https://prosyo.com/tools/domain-health-checker/). |

Other signs are a sudden drop in replies across every campaign at once, a jump in bounces from business domains while Gmail addresses still deliver, and your own test emails disappearing.

## If you are listed on a major list: a 48-hour plan

1. **Hour 0: pause sending** from the affected domain or IP. Continuing makes it worse.
2. **Hour 1: find the cause.** Check sent folders and sending logs for messages you did not write; change mailbox passwords and revoke unknown app connections; look at the last list you uploaded and its bounce rate.
3. **Hour 2: fix it.** Secure accounts, remove the bad list, disable vulnerable forms.
4. **Hour 3: request removal** on each list that requires it, explaining briefly what happened and what you changed.
5. **Day 1 to 2: recheck** here and on the list’s own site. Keep everything paused until you are delisted.
6. **Afterwards: restart slowly** with your best, cleanest contacts and a fraction of the previous volume, then ramp back up over a week or two.

## Free reputation tools from the big providers

Blocklists are one view of reputation. Two free tools show how the largest mailbox providers see you:

- **Google Postmaster Tools** shows your domain’s reputation at Gmail, spam complaint rates, and authentication results, once you send enough daily volume to Gmail users and verify the domain.
- **Microsoft SNDS** (Smart Network Data Services) shows data for IP addresses you control that send to Outlook.com. It is most useful if you run your own sending IPs.

For most cold email teams sending through Google Workspace or Microsoft 365, Postmaster Tools on each sending domain plus a regular blocklist check covers the essentials.

## Blacklists versus spam-folder placement

Being clean on every blocklist does not guarantee the inbox. Gmail and Microsoft rely mostly on their own internal reputation systems, built from how their users react to your mail: opens, replies, deletions without reading and spam reports. Blocklists matter most for business mail servers and smaller providers that use them directly. Think of this checker as ruling out one serious cause of delivery failure, and the [Domain Health Checker](https://prosyo.com/tools/domain-health-checker/) as the broader test.

## How DNS blocklists work

A DNSBL is queried like any other DNS name. To check the IP `203.0.113.10` on a list at `bl.example.org`, a mail server reverses the IP’s numbers and looks up `10.113.0.203.bl.example.org`. If the answer is an address in the `127.0.0.x` range, the IP is listed; the last number often encodes the reason. If there is no answer, it is not listed. Domain lists work the same way with the domain name in front of the list’s zone. This tool runs exactly those queries over DNS-over-HTTPS and interprets the answers, including the special codes that mean “query refused”.

## Domain lists versus IP lists: which affects you?

If you send cold email through Google Workspace or Microsoft 365, the IP addresses belong to Google or Microsoft. They are shared by huge numbers of senders and are actively managed, so IP listings that affect you are rare and short-lived. Your **domain** is what you control and what follows you everywhere: domain lists such as Spamhaus DBL, SURBL and URIBL can list it if it appears in spam reports or in links inside spam. For most outbound teams, a domain listing is the one to watch.

If you send through your own servers or a dedicated IP at an email service, IP lists matter much more, because that IP’s reputation is entirely yours.

## Links in your emails can get you listed too

Domain blocklists look at every domain mentioned in a message, especially in links. If you link to a domain that is listed (a URL shortener that spammers abuse, a tracking domain shared with bad senders, or a partner’s compromised site), your message is scored against that listing. Keep first emails link-free, use your own domain for any link you include, and set up a custom tracking domain if your outreach tool uses link tracking.

## Glossary

- **DNSBL / RBL**: a DNS-based blocklist (also called a real-time blackhole list).
- **Spam trap**: an address that exists only to catch senders using poor-quality lists.
- **Delisting**: removal from a blocklist, automatic or on request.
- **Shared IP**: a sending IP used by many customers of the same provider.
- **Return code**: the 127.0.0.x answer that indicates a listing and often its reason.

## A weekly blocklist routine

For teams sending cold email every day, a two-minute weekly routine catches problems early: run this checker on each sending domain, glance at bounce rates per inbox, and check Google Postmaster Tools for any domain that sends to many Gmail users. If anything changes, pause that domain while you investigate, and let the others carry the volume.

## How Prosyo helps

Prosyo verifies contact details before anything sends and only charges for contacts that verify, sends from your own mailboxes at safe daily volumes, and stops every sequence the moment someone replies. Those are the habits that keep domains off blocklists. [Try it free for 7 days](https://prosyo.com/pricing/).

## Related free tools

These tools are often used together with the Blacklist Checker. All of them are free, and the checkers and calculators run instantly in your browser.

- [Domain Health Checker](https://prosyo.com/tools/domain-health-checker/): Score your sending domain on MX, SPF, DKIM, DMARC, BIMI, MTA-STS and blocklists in one click, with a fix for everything that fails.
- [Email Verifier](https://prosyo.com/tools/email-verifier/): Check up to 50 addresses for syntax, mail servers, disposable and role-based addresses and typos, then export a CSV.
- [Warm-up Planner](https://prosyo.com/tools/email-warmup-planner/): Get a day-by-day warm-up and ramp schedule for a new inbox or domain.
- [Spam Word Checker](https://prosyo.com/tools/spam-word-checker/): Highlight every spam-trigger word in your email by category, with plainer alternatives.

## Frequently asked questions

### How do I check if my domain is blacklisted?

Enter the domain in the checker above. It checks the domain on domain blocklists and the IP addresses of its mail servers on IP blocklists, and shows every result separately.

### How do I check if an IP address is on a blacklist?

Enter the IPv4 address. The tool checks it against widely used IP blocklists such as SpamCop, PSBL, UCEPROTECT, Mailspike, NiX Spam, DroneBL and Spamhaus ZEN where public queries are allowed.

### Why does Spamhaus show as not checkable?

Spamhaus refuses queries from large public DNS resolvers, which browser tools have to use. Check Spamhaus listings directly on the Spamhaus website.

### How long does it take to get delisted?

Many lists remove entries automatically within a day once the problem stops; others need a removal request and take one to several days. Fix the cause first, or you will be listed again.

### Can a blacklist affect my cold email even if I use Gmail or Microsoft 365?

Their shared sending IPs are rarely listed for long, but your domain can still be listed on domain blocklists if it appears in spam reports or links. Domain listings follow you to any provider.

### Does being on a blacklist mean my email goes to spam everywhere?

Not necessarily. It depends on which list and which receivers use it. Major lists affect many business mail servers; minor lists affect few. Gmail and Microsoft rely mainly on their own reputation data.

### What is the difference between a domain blacklist and an IP blacklist?

An IP blacklist lists the address of a sending server; it affects only mail sent from that IP. A domain blacklist lists a domain name; it affects any message that contains the domain, in the From address or in links, from any server.

### Can I be blacklisted for sending cold email?

Yes, if lists are poor quality or volume is too high. Spam traps hide in scraped and old lists, and complaints rise when messages are irrelevant. Verify every list, keep bounce rates low, send modest volumes per mailbox and write to people your offer genuinely fits.

### How often should I check for blacklisting?

Weekly while you are actively sending cold email, and immediately if bounces or rejections jump. A quick check takes seconds and catches problems before they spread across campaigns.

### Is this blacklist checker free?

Yes, with no sign-up. Queries run from your browser over DNS-over-HTTPS and nothing is stored.

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