How to Check if Your Domain Has Been Blacklisted (And What to Do About It)

Marcus ran a small architecture firm in Portland. Every Tuesday morning he sent a newsletter to 4,200 subscribers, mostly past clients and referral partners. He'd been building that list for two years. It was the engine behind most of his new project inquiries.

One Tuesday, by noon, he had a response rate of zero. Not low. Zero.

He checked the usual suspects: subject line, send time, list segmentation. Everything looked fine. Then a subscriber, a contractor he'd worked with for years, emailed him directly. "Hey, I never get your emails anymore. Checked my spam folder. They're not even there."

Not in spam. Not bounced. Just gone.

When Marcus finally ran his domain through a blacklist checker, he found it listed on three separate databases. He'd never heard of any of them. He hadn't done anything wrong. But his emails were being silently dropped at the server level before they ever reached a spam folder.

That's the thing about blacklists. They don't send you a notice. They just cut you off.

The Three Types of Blacklists You Need to Know

Here's what most people assume when they hear "blacklist": email spam filters. And that's fair. Email blacklists are the most common and the most immediately painful. But they're only one of three categories. And the other two are the ones that blindside you, because most guides don't cover them at all.

1. Email Blacklists (DNSBLs)

These are the most common and the most immediately painful. DNS-based blacklists, or DNSBLs, are databases that mail servers query in real time to decide whether to accept incoming messages.

Spamhaus is the one that matters most. They operate three distinct categories:

• SBL (Spam Block List): Active spam sources. If your domain is sending spam or hosted on infrastructure that is, you end up here.
• XBL (Exploits Block List): Compromised machines, infected servers, open proxies. If your hosting environment has been hijacked, this is where you land.
• DBL (Domain Block List): Domains actively used in spam, even if just as links in a spam email rather than the sending domain.

Barracuda Central maintains a separate blacklist that many corporate mail servers use. MXToolbox covers over 100 blacklists simultaneously, which is why it's the practical starting point for any check.

Once you're on a major DNSBL, email deliverability drops to near-zero for affected domains. Delisting from the Spamhaus SBL alone can take 24-72 hours with a manual review process. That's time your business doesn't have. Every hour on a list is emails that aren't arriving, conversations that aren't starting, deals that aren't closing.

But at least with email blacklists, there's a clear mechanism and a clear fix. The next type is harder to detect and harder to recover from.

2. Web and Browser Blacklists

Most people never think about browser blacklists until they see the red screen. If your domain appears on Google Safe Browsing, your site gets flagged with a red warning screen before visitors even land on it. Chrome, Firefox, and Safari all use this database.

This happens when:

• Your site has been hacked and is distributing malware
• Your domain was previously used for phishing
• Your hosting server (shared IP) got flagged through no fault of your own

A browser blacklist warning isn't just reputation damage. It's a wall. Most users won't click through it. They close the tab and move on. You never find out they tried to reach you.

And then there's the third type. The one that's quieter than either of these. The one where you don't get a red screen, you don't get a bounce notification. You just stop existing.

3. AI Search Exclusion

This one is newer, and most domain owners have no idea it exists. AI search engines like Perplexity and ChatGPT's Browse feature maintain trust signals about domains. Domains associated with spam, malware, or thin content get deprioritized or excluded from citations entirely.

This matters because AI citations are becoming a primary discovery mechanism. A domain that gets excluded doesn't just lose visibility in traditional search. It disappears from the sources these systems draw on when someone asks a question in your space.

Think about what that means. Someone is asking a question you can answer better than anyone. The AI system pulls from five sources. Yours isn't one of them. Not because your answer is wrong, but because your domain doesn't pass the trust check.

The distinction between blacklisting and penalization matters here. A blacklist is a hard block. A penalty is a signal degradation. Google Search Console issues manual action penalties that are domain-specific, but AI search deprioritization is subtler and harder to detect. You won't get a notification. You'll just notice that your domain never gets cited.

How to Check Each Type

Checking Email Blacklists

Start with MXToolbox. Go to mxtoolbox.com/blacklists.aspx and enter your domain. It runs your domain against 100+ blacklists simultaneously and flags any hits with the specific list name.

Also check:

• Spamhaus directly: spamhaus.org/lookup/. Check both your domain and your sending IP address.
• Barracuda: barracudacentral.org/lookups. Enter your IP (not just your domain).
• MultiRBL: multirbl.valli.org. Covers additional databases MXToolbox misses.

One thing people miss: check your IP address, not just your domain. If you're on shared hosting, another customer on the same server may have gotten the IP blacklisted. Your domain is clean, but your mail is still being blocked.

Checking Web and Browser Blacklists

Google has a dedicated tool: transparencyreport.google.com/safe-browsing/search. Enter your domain and it will tell you if Google Safe Browsing has flagged it.

For a broader check, use:

• Sucuri SiteCheck: sitecheck.sucuri.net. Scans your site and cross-references multiple security databases.
• VirusTotal: virustotal.com. Enter your URL and it checks against 70+ security vendors simultaneously.

If you're finding flags here, the issue is usually a compromised server or a domain that was previously used for malicious purposes. Both are fixable, but the path is different. And that's actually the important distinction: knowing which type of problem you have determines which fix applies.

Checking for AI Search Trust Signals

This one is harder to check directly because AI search systems don't publish their trust criteria. But there are proxy signals worth monitoring:

• Run your domain through Ahrefs Site Explorer or Semrush and look for any manual penalties in Google Search Console.
• Check whether your domain appears in any known spam domain databases using Spamhaus DBL.
• Search for your domain name in ChatGPT or Perplexity and see whether it's cited in responses for your topic area. If competitors in your space appear but you don't, that's a signal worth investigating.

The False-Positive Problem

So you ran the checks. You found a listing. Before you panic, read this section. Because here's something most blacklist guides skip entirely: a significant portion of blacklist entries are wrong.

Shared hosting is the most common cause. If your website sits on a shared IP address alongside hundreds of other sites, and one of those sites sends spam, the entire IP block can get flagged. Your domain is collateral damage.

This happens to legitimate businesses regularly. You wake up one morning with a blacklisted IP you share with a domain you've never heard of.

The same problem exists with purchased domains. If you bought a domain with existing history, that history came with it. Previous owners may have used it for spam, and the domain's reputation reflects that past, not your current use.

Identifying false positives matters because the delisting process is different. For a genuine violation, you need to fix the underlying problem first. For a false positive, you're submitting a request that says "I'm not the one who did this and I can prove it."

And that's where the real work begins. Because knowing you're on a list is only half the problem. Getting off it requires a different set of steps for each type.

How to Get Delisted

The process differs by list type.

Email Blacklists

First, fix the actual problem. Submitting a delisting request before addressing the root cause will get you re-listed within days. Common root causes:

• Compromised email account sending spam from your domain
• Open mail relay on your server
• Weak email authentication (missing or misconfigured SPF, DKIM, DMARC records)
• Shared hosting IP that was flagged (in this case, contact your host to request a new IP)

Once the problem is fixed:

Spamhaus: Use their removal center at spamhaus.org. SBL removals require manual review and take 24-72 hours. XBL and DBL removals can be automatic if the issue is resolved.

Barracuda: barracudacentral.org/rbl/removal-request. They offer a request form. Approval can take 24-48 hours.

Other lists: Each has its own process. MXToolbox's results page links directly to the removal form for each blacklist it detects.

Browser and Web Blacklists

For Google Safe Browsing, clean the malware or phishing content from your site first, then request a review through Google Search Console under Security Issues. Resolution time varies but is typically 1-3 days once the issue is resolved.

For other security vendors, Sucuri and VirusTotal both provide direct links to each vendor's removal process in their scan results.

AI Search Trust Signals

This is the hardest to fix because there's no single submission form. AI search trust is rebuilt through consistent, quality content and clean technical signals over time. The practical steps:

• Fix any underlying issues in Google Search Console
• Ensure your domain has no active security flags
• Publish structured, useful content regularly
• Check that your domain's structured data is correct and complete

Recovery here is measured in weeks, not hours.

The Difference Between Being Blacklisted and Being Penalized

Before you start submitting removal requests, make sure you know which problem you actually have. This distinction matters, and most guides conflate the two.

A blacklist is a hard, binary block. Your domain is either on the list or it isn't. Mail servers refuse delivery, browsers show warnings, or AI systems exclude your domain. The block is immediate and severe.

A penalty (in the Google Search Console sense) is a signal degradation. Your domain isn't blocked. It's just ranked lower, or certain pages are demoted. Penalties require their own resolution process through Search Console's manual actions section.

Some domains have both. They've been flagged for email spam AND received a manual penalty for thin content. These need separate fixes for separate systems.

Knowing which one you're dealing with tells you where to look and what to fix. Don't spend three days submitting email blacklist removal requests if your problem is a Google manual action.

Prevention Is Easier Than Recovery

Here's what I wish someone had told Marcus before that Tuesday morning. Most blacklist entries are preventable. Not all of them. But enough that the prevention work is worth far more than the recovery work.

The pattern shows up again and again. The domains that end up on blacklists share a profile. No active content. Email authentication that's incomplete or absent. Sitting dark on shared hosting. No visible signals of active, legitimate ownership. In other words, the domains that look like they belong to nobody are the ones that get treated like they belong to nobody.

These are the same domains that are parked or dormant. The infrastructure that serves them is often shared with spammers. And without a reputation to protect them, the systems that monitor for abuse don't have a reason to give them the benefit of the doubt.

A domain with active signals, published content, proper email authentication (SPF, DKIM, DMARC), and structured data sends a different signal to every system checking it. Not just to humans. To the blacklist monitoring systems that decide whether to flag it.

Warming a domain doesn't just build visibility. It builds the kind of clean technical record that makes it much harder to end up on any of these lists in the first place. The domain health check beyond renewal goes deeper on what a complete signal audit looks like, but the principle is simple: visible, active domains are harder to mistake for spam infrastructure.

If you're curious how an expired domain creates this same risk not just for itself but for every other domain you own, that's the scenario Can an Expired Domain Hurt Your Other Domains or Brand? works through in detail.

An active domain has a content record, clean email authentication, and structured data that confirms legitimate ownership. These are exactly the signals blacklist monitoring systems look for when deciding whether a domain belongs on a list. Prevention is the frame. The system's continuous warming is the mechanism. A domain sitting dark right now doesn't have the visibility to protect itself. What is SiteWarming?

Related reading:

• Email deliverability starts before you hit send: the pre-send checklist that prevents most deliverability failures
• Trust is a system: why trust is built through infrastructure signals, not just content
• What happens when a domain expires: what's actually happening to your domain between renewal dates
• Can an expired domain hurt your brand?: the collateral damage scenario for multi-domain owners

Image Credits

Photo by Ludovic Delot on Unsplash