April 9, 2026Updated April 10, 20268 min readby Vladimir Kamenev

Free Domain Blacklist Checker — Scan 30 Email Blacklists in Seconds

The one-line answer

WeLead Lab's free domain blacklist checker scans your domain's mail server IP against 30 major DNS-based blacklists — including Spamhaus, Barracuda, SpamCop, SORBS, and UCEPROTECT — in 5 to 10 seconds. No signup, no credit card, no limits.

Why blacklists matter

Roughly 21% of legitimate emails never reach the inbox, and blacklists are one of the biggest reasons why. A single listing on a respected DNS blacklist can quietly route every email you send straight to the spam folder — or cause it to bounce entirely. Invoices go missing. Sales quotes vanish. Password resets never arrive.

The worst part is that most businesses have no idea they're on a blacklist until customers complain. By the time you hear "I never got your email," you may have already lost deals, damaged client trust, and trained mail providers to treat your domain as suspicious. Email deliverability is one of those things you only notice when it's broken.

That's why running a blacklist checker regularly — not just once a year — is one of the cheapest and highest-impact things you can do for your business communication.

What is a DNS-based blacklist (RBL)?

A DNS blacklist, also called an RBL (Realtime Blackhole List) or DNSBL, is a database of IP addresses that have been flagged for sending spam, hosting malware, running open relays, or otherwise behaving badly. These lists are distributed using the DNS protocol, which is why they're fast and cheap for mail servers to query.

Here's what happens every time someone sends you an email:

Your mail server receives a connection from a sending IP.
Before accepting the message, it queries multiple DNS blacklists to see if the sender's IP is listed.
If the IP appears on one or more RBLs, the server either rejects the message outright or routes it to spam.

This all happens in milliseconds, invisible to both sender and recipient. The RBL ecosystem is what keeps most of the world's spam out of inboxes — but it also means that if your IP gets listed, your legitimate mail becomes collateral damage.

The 30 blacklists we check

Our free domain blacklist checker queries 30 of the most widely used DNS blacklists in parallel. Here's the full list:

#	Blacklist	Category	Notes
1	Spamhaus ZEN	Major	Most widely trusted; combines SBL, XBL, PBL
2	Spamhaus SBL	Major	Spam sources
3	Spamhaus XBL	Major	Exploited systems
4	Spamhaus PBL	Major	Policy block list
5	Barracuda	Major	Used by Barracuda appliances worldwide
6	SpamCop	Major	User-reported spam
7	SORBS	Major	Multi-zone blocklist
8	UCEPROTECT Level 1	Major	Single-IP listings
9	UCEPROTECT Level 2	Major	Network-wide listings
10	UCEPROTECT Level 3	Major	ASN-wide listings
11	PSBL	Industry	Passive Spam Block List
12	SpamRATS	Industry	Reputation-based RBL
13	CBL Abuseat	Industry	Composite Blocking List
14	DroneBL	Industry	Known botnet drones
15	Mailspike	Specialized	Reputation + behavioral
16	InterServer RBL	Specialized	Hosting-focused
17	Blocklist.de	Specialized	Attack and abuse reports
18	Mailhaus	Specialized	Heuristic blocklist
19	s5h.net	Specialized	Tornevall's list
20	0spam	Specialized	Community-driven
21	NoSolicitado	Specialized	Spanish-language focus
22	Manitu (ix.dnsbl)	International	Popular in Germany
23	VirBL	International	Virus-sending IPs
24	Abuse.ro	International	Romanian RBL
25	Backscatterer	Specialized	Misdirected bounces
26	LashBack UBL	Specialized	Unsubscribe abuse
27	RATS Dyna	Industry	Dynamic IP ranges
28	RATS NoPtr	Industry	Missing reverse DNS
29	Truncate	Specialized	High-confidence spam
30	WPBL	Specialized	Weighted private block list

If any of these lists have your mail server IP flagged, your email deliverability is almost certainly suffering. Some listings (like Spamhaus SBL) are catastrophic; others (like UCEPROTECT L3) are more advisory. Our blacklist checker shows you exactly which ones and how serious each is.

What our free blacklist checker does

Here's the technical breakdown of what happens when you run the tool:

Resolves your domain's MX record — We look up your domain's mail exchangers and pull the IP address of your primary mail server. You just paste the domain; we handle the DNS.

Queries all 30 blacklists in parallel — Each RBL gets a simultaneous DNS query, so the total scan takes 5 to 10 seconds instead of a couple minutes.

Reports every listing — If your IP appears on any of the 30 lists, we show you which ones, along with a link to each provider's delisting page.

Checks reverse DNS — We also check whether your IP has proper PTR records, since missing rDNS is a common reason mail gets rejected.

No signup, no rate limits — Run it as many times as you need.

How to use it

Running the free domain blacklist checker takes three steps:

Go to weleadlab.com/website-analyzer

Enter your domain (for example, yourcompany.com — not the IP address, just the domain)

Read the results — Within 10 seconds you'll see all 30 RBLs checked, with clear green/red status for each

That's it. If everything is clean, you'll get a green "not listed" result for all 30 DNS blacklists. If anything is flagged, you'll see exactly which lists and how to fix it.

What to do if you're blacklisted

Finding out you're on a blacklist is stressful, but the fix is usually straightforward. Here's the playbook:

Identify the specific list — Each RBL has its own delisting process. Click through to the blacklist's website (our tool links directly) and read their removal instructions. Some auto-delist within 24-72 hours once the issue stops; others require you to submit a request.

Stop whatever caused the listing — Delisting without fixing the root cause is pointless; you'll just get re-listed within hours. Common culprits include a compromised WordPress site, a hacked email account, or an open SMTP relay.

Request delisting — After fixing the cause, submit the removal request. Be honest about what happened; blacklist operators have heard every excuse and they respect owners who take responsibility.

Fix your SPF, DKIM, and DMARC — The overwhelming majority of blacklist listings trace back to poor email authentication. If your domain has weak SPF and no DMARC, attackers can spoof you freely, and your real mail gets caught in the crossfire.

Monitor for re-listing — Run the blacklist checker again 24 hours later, then weekly for the next month, to make sure you stay clean.

Common causes of blacklisting

Understanding why IPs get listed helps you prevent it. In our experience, these are the top reasons:

A compromised WordPress site sending spam — Outdated plugins are the #1 attack vector. A single vulnerable form plugin can turn your hosting account into a spam cannon overnight.

Shared hosting where a neighbor was spamming — If you share an IP with other tenants on cheap hosting, their bad behavior can get your mail blocked. This is one reason dedicated IPs matter.

An email list purchased from a broker — Purchased lists are radioactive. Spam traps get hit, complaints pile up, and you land on Spamhaus SBL within days.

Phishing or abuse complaints — Users reporting your emails as phishing — even incorrectly — can trigger listings on user-driven lists like SpamCop.

High bounce rates — Sending to stale lists with lots of dead addresses signals spammer behavior to mailbox providers and RBLs alike.

Open SMTP relay or misconfigured server — An accidentally open relay gets discovered and weaponized within hours. Always require authentication.

Prevention: stay off blacklists forever

Running a blacklist checker is defense. Prevention is even cheaper. Build these habits:

Set up SPF, DKIM, and DMARC properly — This is non-negotiable in 2026. Gmail and Yahoo actively reject mail without proper authentication, and RBLs use auth failures as spam signals. Start with an SPF record, enable DKIM signing on your mail server, then add a DMARC policy (begin with p=none and ramp up to p=reject).

Use double opt-in for email lists — Every subscriber should confirm their email address before you add them to any marketing list. This eliminates spam traps and typo-addresses.

Monitor your sender reputation — Tools like Google Postmaster Tools and Microsoft SNDS show how Gmail and Outlook view your domain. Check them weekly.

Prune inactive subscribers — If someone hasn't opened an email in 180 days, stop mailing them. High engagement = high inbox placement.

Keep your software patched — WordPress, plugins, mail server software. Most compromises come from known, patchable vulnerabilities.

Run the blacklist checker monthly — Catching a listing in its first 24 hours is infinitely easier than catching it after a month of bounces.

Try the free domain blacklist checker now

Stop guessing about your email deliverability. Run the free domain blacklist checker at weleadlab.com/website-analyzer and get a complete report across 30 DNS blacklists in under 10 seconds. No signup, no limits, no nonsense.

FAQ

Is the blacklist checker actually free? Yes. It's completely free, no account required, no rate limits. We built it because checking 30 RBLs manually is painful and the paid alternatives are overkill for most small businesses. How often should I run a blacklist check? For most businesses, monthly is enough. If you send high volumes of marketing email, run it weekly. If you just discovered a deliverability problem, run it immediately — then again 24 hours after any fixes. What's the difference between Spamhaus and UCEPROTECT? Spamhaus is the most trusted and widely used RBL in the world; a listing there is a big deal and mail providers almost universally respect it. UCEPROTECT runs three levels of increasing aggression — L1 is specific, L2 and L3 escalate to network and ASN-wide blocks and are less strictly enforced by major providers. Can I get delisted from Spamhaus? Yes, usually within 24-72 hours after you fix the underlying issue. Spamhaus is actually one of the more responsive RBLs if you engage with their process honestly. Auto-delistings (like SBL expirations) happen without any action once the spam stops. Why does my IP show on a blacklist even though I don't send spam? Three common reasons: (1) your web host or domain was compromised and you didn't notice, (2) you're on shared hosting with a neighbor who is spamming, or (3) you're on a dynamic IP range that some RBLs block by default. Our free domain blacklist checker tells you which list flagged you so you can diagnose the cause.