How to Check If Your Email Domain Is Blacklisted and What to Do About It

By Puzzle Inbox Team · Apr 5, 2026 · 9 min read

Your domain might be on an email blacklist without you knowing. Here's how to check, how to get delisted, and how to prevent it from happening again.

What Email Blacklists Are and Why They Matter

An email blacklist is a database of domains and IP addresses that have been flagged for sending spam or suspicious email. When your domain appears on a blacklist, email providers like Gmail and Outlook use that information to decide whether your emails reach the inbox or go straight to spam.

Not all blacklists are equal. Some are widely used by major email providers and will tank your deliverability overnight. Others are minor lists that barely affect your sending. Knowing which blacklists matter, and regularly checking whether you're on them, is a basic hygiene practice for anyone running cold email.

The tricky part: you can end up on a blacklist without doing anything obviously wrong. A high bounce rate from a bad list, a few spam complaints from poorly targeted emails, a compromised inbox sending spam without your knowledge, or even inheriting a blacklisted domain from a previous owner. By the time you notice your reply rates dropping, you might have been listed for weeks.

The Major Blacklists That Actually Affect Deliverability

There are hundreds of email blacklists, but only a handful are widely referenced by major email providers. These are the ones that actually matter for cold email deliverability.

Spamhaus

Spamhaus is the most influential email blacklist in the world. Their databases (SBL, XBL, PBL, DBL) are used by the majority of email providers and corporate email servers to filter incoming mail. If your domain is on Spamhaus, your deliverability is essentially zero. Spamhaus listings are serious and require formal delisting requests with evidence that you've fixed the underlying problem.

Barracuda (BRBL)

Barracuda maintains its own blacklist based on spam data from their network of email security appliances used by thousands of businesses. A Barracuda listing primarily affects your emails to companies using Barracuda email security (which is common in mid-size and enterprise environments). Delisting is usually straightforward through their self-service removal tool.

SpamCop

SpamCop is a user-driven reporting system. When email recipients report spam to SpamCop, the sending IP and domain can be added to their blacklist. SpamCop listings are typically temporary and expire after 24 to 48 hours if no new reports come in. However, repeated listings indicate a systemic problem with your sending practices.

SORBS (Spam and Open Relay Blocking System)

SORBS maintains multiple lists including lists for spam sources, open relays, and dynamically assigned IP ranges. SORBS listings can be sticky and sometimes require a small donation to expedite delisting. The impact on deliverability varies, but it's worth monitoring.

Composite Blocking List (CBL)

The CBL is part of the Spamhaus XBL and focuses on IP addresses that show signs of bot or malware infection. If your IP appears on the CBL, it usually means your email infrastructure has been compromised or is sending suspicious traffic patterns.

How to Check If You're Blacklisted

Regular blacklist checking should be part of your cold email operations routine. Run checks weekly at minimum, and immediately if you notice a sudden drop in reply rates or an increase in bounce rates.

MXToolbox

MXToolbox is the industry standard for blacklist checking. Their free blacklist lookup queries your domain or IP against 100+ blacklists simultaneously. Enter your sending domain, click check, and you'll see green (clear) or red (listed) results for each blacklist. It takes about 30 seconds and should be a weekly habit.

PuzzleInbox Blacklist Checker

Our free blacklist checker queries the major blacklists that specifically affect cold email deliverability. It's designed for cold email senders, so it focuses on the lists that matter most for your use case rather than showing you 100+ lists that include irrelevant databases.

Google Postmaster Tools

While not a blacklist checker per se, Google Postmaster Tools shows you your domain reputation directly from Google's perspective. If your reputation drops from "High" to "Low" suddenly, a blacklisting could be the cause. Set this up for every domain you send cold email from.

What to Do If You're Blacklisted

Finding your domain on a blacklist isn't the end of the world, but it does require immediate action. Here's the step-by-step process.

Step 1: Stop Sending Cold Email Immediately

The moment you discover a blacklisting, pause all cold email campaigns from the affected domain. Continuing to send while listed makes the problem worse. Every email you send while blacklisted either bounces, goes to spam, or generates more negative signals that reinforce the listing.

Step 2: Identify the Cause

Blacklists don't list domains randomly. Something triggered it. The most common causes for cold email senders:

• High bounce rate: Sending to unverified email addresses. If more than 2 to 3% of your emails bounce, you're at risk. The fix: verify every email address before sending.
• Spam complaints: Too many recipients marking your emails as spam. This usually means your targeting is too broad or your copy is too aggressive. The fix: tighten your targeting and soften your approach.
• Compromised account: Someone gained access to one of your email accounts and used it to send spam. Check your account activity logs. The fix: change passwords, enable 2FA, and audit account access.
• Spam trap hits: You sent an email to a spam trap address. These are addresses maintained by anti-spam organizations specifically to catch senders using bad lists. The fix: use verified data sources and clean your lists regularly.
• Sending volume spikes: A sudden increase in sending volume can trigger blacklist systems. The fix: ramp volume gradually and stay within per-inbox daily limits.

Step 3: Submit a Delisting Request

Each blacklist has its own delisting process. Here's how to handle the major ones:

Spamhaus: Visit their blocklist removal center. You'll need to explain what caused the listing and what steps you've taken to fix it. Spamhaus reviews requests manually, so be thorough and honest. Do not submit repeated requests if denied. Fix the problem first, then try again.

Barracuda: Use their self-service removal request form. Barracuda listings are usually removed within 12 to 24 hours after the request.

SpamCop: SpamCop listings expire automatically after 24 to 48 hours if no new spam reports come in. You don't need to request removal. Just stop the behavior that triggered the reports.

SORBS: Check their FAQ for specific delisting procedures. Some SORBS lists require a small fee for expedited removal.

Step 4: Reduce Volume and Rebuild

After delisting, don't immediately jump back to full sending volume. Treat the domain like it's been through a reputation reset:

• Run warmup-only activity for 7 to 14 days
• Resume cold email at 25% of your previous volume
• Monitor blacklists and Google Postmaster Tools daily
• Gradually increase volume over 2 to 4 weeks if all signals are positive

When to Abandon a Domain vs. Try to Recover It

Sometimes the right move is to walk away from a blacklisted domain and start fresh. Here's how to decide.

Try to recover when:

• This is your first blacklisting on this domain
• The cause was a one-time mistake (bad list, accidental volume spike)
• The listing was on a minor blacklist (not Spamhaus)
• The domain has significant brand value or history

Abandon the domain when:

• The domain has been listed on Spamhaus multiple times
• Delisting requests have been denied after genuine remediation
• The domain's Google Postmaster reputation is stuck at "Bad" for more than 6 weeks
• The domain is a cold email sending domain (not your primary business domain) and replacing it is easier than recovering it

This is why you should never send cold email from your primary business domain. If a cold email domain gets permanently blacklisted, you retire it and start a new one. If your primary business domain gets blacklisted, your entire company's email communication is affected.

Prevention: How to Stay Off Blacklists

Prevention is dramatically easier than recovery. These practices keep your domains off blacklists in the first place.

Verify Every Email List

Run every email list through a verification service before sending. ZeroBounce, MillionVerifier, Bouncer, or any reputable email verification tool. Remove invalid addresses, risky addresses, and role-based addresses (info@, support@, admin@). Re-verify any list that's more than 30 days old.

Proper Warmup

Warm every inbox for at least 14 days before sending cold email. Maintain warmup activity alongside active sending. Never skip this step, even if you've done it before on other domains.

Volume Limits

Stay at 15 to 20 emails per inbox per day for Google Workspace. Use 3 inboxes per domain maximum. Scale by adding domains and inboxes, not by increasing per-inbox volume. These limits exist because exceeding them is one of the fastest paths to a blacklisting.

Monitor Regularly

Check your sending domains against major blacklists weekly. Use our blacklist checker and MXToolbox. Set up Google Postmaster Tools for every sending domain. Catch problems early before they become permanent reputation damage.

Clean Sending Practices

No tracking pixels. No links in the first email. Plain text emails under 100 words. An unsubscribe mechanism in every email. These aren't just deliverability tips. They're blacklist prevention.