If your emails are suddenly landing in spam folders or not being delivered at all, there is a good chance your domain or sending IP address has ended up on an email blacklist. Blacklists are one of the most common causes of email deliverability problems, and getting listed can happen without any malicious intent on your part.

This guide covers how email blacklists work, how to check whether you are listed, step-by-step removal procedures for the major blacklists, and strategies to prevent being listed again.

What Email Blacklists Are and How They Work#

An email blacklist (also called a DNSBL, or DNS-based Blackhole List) is a real-time database of IP addresses and domains that have been identified as sources of spam or malicious email. Email servers around the world query these blacklists when receiving inbound email to decide whether to accept, reject, or flag a message.

The process works like this:

Your mail server sends an email to a recipient.
The recipient's mail server extracts your sending IP address from the email headers.
The receiving server performs a DNS lookup against one or more blacklists, asking: "Is this IP address listed?"
If the IP is listed, the receiving server applies its configured policy: reject the message, send it to spam, or add a spam score penalty.

A single blacklist listing does not necessarily mean all your email is blocked. Different email providers check different blacklists and apply different weight to each. However, being listed on a major blacklist like Spamhaus or Barracuda can have a significant impact on deliverability across a wide range of recipients.

Major Email Blacklists#

Not all blacklists carry equal weight. Here are the ones that matter most.

Spamhaus#

Spamhaus operates several lists that are queried by the majority of the world's email servers:

SBL (Spamhaus Block List): IP addresses involved in sending spam. This is the main list.
XBL (Exploits Block List): IP addresses of hijacked machines, open proxies, and compromised servers.
PBL (Policy Block List): IP ranges that should not be sending email directly (residential IPs, dynamic ranges).
DBL (Domain Block List): Domains (not IPs) that appear in spam messages.

Spamhaus is widely considered the most influential blacklist. Being listed here has the broadest deliverability impact.

Barracuda (BRBL)#

Barracuda Networks maintains its own blacklist, the Barracuda Reputation Block List. It is used by Barracuda appliances and a significant number of email servers that integrate its data. Barracuda tends to list IPs that send large volumes of spam or have poor sending practices.

SpamCop#

SpamCop is a user-driven blacklist. Recipients report spam through the SpamCop system, which traces the message back to the sending IP and adds it to the blocklist. SpamCop listings are typically short-lived (24-48 hours) and expire automatically if no new reports are received.

SORBS (Spam and Open Relay Blocking System)#

SORBS maintains multiple lists covering spam sources, open relays, open proxies, and dynamic IP ranges. SORBS listings can be persistent and may require manual delisting requests.

SpamRATS#

SpamRATS focuses on three categories:

RATS-Dyna: Dynamic or residential IP addresses.
RATS-NoPtr: IP addresses without valid reverse DNS (PTR) records.
RATS-Spam: IP addresses caught sending spam.

SpamRATS listings often indicate infrastructure configuration issues rather than active spam sending.

Other Notable Blacklists#

UCEPROTECT: Operates three levels, with Level 3 listing entire ISP ranges. Can be difficult to delist from.
invaluement: Focuses on snowshoe spam (low-volume spam distributed across many IPs).
Passive Spam Block List (PSBL): Automated list based on spam trap hits.

Why You Might Be Blacklisted#

Understanding the root cause is essential before attempting removal. Blacklist operators will deny your delisting request if you have not fixed the underlying problem.

Compromised Server or Account#

If your mail server, web server, or any user account on your system has been compromised, the attacker may be using your infrastructure to send spam. This is one of the most common reasons for blacklisting, especially on shared hosting.

Signs: Sudden spike in outbound email volume, unfamiliar messages in your outbound queue, bounce-back notifications for messages you did not send.

Sending to Purchased or Scraped Email Lists#

Purchased email lists almost always contain spam traps: email addresses specifically created to catch senders who do not use opt-in practices. Hitting even a single spam trap can get you blacklisted.

High Complaint Rate#

When recipients mark your email as spam, their email provider tracks this. If your complaint rate exceeds roughly 0.1% (1 complaint per 1,000 emails), you are at risk of blacklisting. This happens even with legitimate opt-in lists if your content is not meeting subscriber expectations.

Open Relay Configuration#

An open relay is a mail server that accepts and forwards email from any sender, not just authenticated users. Open relays are exploited by spammers to send bulk email through your infrastructure. Most modern mail server software is configured to prevent this by default, but misconfigurations happen.

Missing or Incorrect DNS Records#

Sending email from an IP address without a valid PTR (reverse DNS) record, or from a domain without proper SPF, DKIM, and DMARC records, can trigger blacklisting. These records are basic signals that your email infrastructure is legitimately configured.

IP Address Reputation Inheritance#

If you are using a new VPS, cloud server, or shared hosting plan, you may inherit the IP reputation of the previous user. If the previous tenant was sending spam, the IP may already be blacklisted when you start using it.

How to Check if You Are Blacklisted#

Method 1: Nova Uptime Email Health Tool#

The fastest way to check your blacklist status is to use Nova Uptime's Email Health Checker. Enter your domain, and the tool performs a comprehensive check that includes:

MX record validation: Confirms your mail servers are properly configured.
SPF record analysis: Checks your SPF policy and evaluates its strength.
DKIM detection: Scans for DKIM signing across common selectors.
DMARC policy review: Evaluates your DMARC configuration.
Blacklist check: Resolves your MX server IP addresses and checks them against major DNS blacklists.

The results include a score breakdown showing your blacklist status with a clear pass/fail for each list checked. If any listings are found, they are identified by name so you know exactly which blacklist to address.

Method 2: Manual DNS Queries#

You can check a specific blacklist manually using dig or nslookup. The process involves reversing your IP address and appending the blacklist's domain.

For example, to check if IP address 203.0.113.50 is listed on Spamhaus SBL:

# Reverse the IP octets and append the blacklist domain
dig +short 50.113.0.203.zen.spamhaus.org

# If listed, you get a response like 127.0.0.2
# If clean, you get no response (NXDOMAIN)

The return codes indicate the specific list:

127.0.0.2 = SBL (Spamhaus Block List)
127.0.0.3 = SBL CSS
127.0.0.4-7 = XBL (Exploits Block List)
127.0.0.10-11 = PBL (Policy Block List)

For domain-based blacklists like Spamhaus DBL:

dig +short yourdomain.com.dbl.spamhaus.org

This manual approach is useful for targeted checking but is tedious when you need to verify against multiple blacklists. Automated tools are significantly more efficient.

Method 3: Check Your Bounce Messages#

Email bounce messages (NDRs) often contain specific information about which blacklist caused the rejection. Look for patterns like:

550 5.7.1 Service unavailable; client [203.0.113.50] blocked using zen.spamhaus.org

These messages tell you exactly which blacklist flagged you and the sending IP that is listed.

Step-by-Step Removal for Major Blacklists#

Before submitting any delisting request, you must fix the underlying problem. If you request removal without fixing the cause, you will be relisted quickly, and repeat listings are harder to remove.

Spamhaus Removal#

Identify the listing: Visit the Spamhaus lookup page and enter your IP or domain.
Read the listing details: Spamhaus provides a reason for the listing, including dates and evidence.
Fix the problem: Secure compromised accounts, close open relays, remove purchased lists, or clean your sending practices.
Request removal: Use the removal link provided on the lookup page. For SBL listings, this opens a removal request form. For XBL listings, removal is typically automatic once the compromised system is secured. PBL listings require contacting your ISP, as they control which IP ranges are listed.
Wait for processing: SBL removal requests are reviewed by humans and may take 24-48 hours.

Note: Spamhaus will not remove a listing if the underlying problem is not fixed. Repeated listing-and-removal cycles result in longer listing durations.

Barracuda Removal#

Check your listing: Visit the Barracuda Central lookup and enter your IP.
Register for an account: Barracuda requires a free account to submit removal requests.
Submit removal request: After logging in, use the removal request form. Include details about what caused the listing and what you have done to fix it.
Processing time: Barracuda typically processes removal requests within 12-24 hours.

Barracuda has a relatively straightforward removal process, but they monitor for re-listing. If the same IP is listed again shortly after removal, subsequent removal requests may be delayed.

SpamCop Removal#

SpamCop listings are designed to expire automatically. If no new spam reports are received for your IP address, the listing typically expires within 24-48 hours.

There is no manual removal process for SpamCop. The best approach is to:

Identify and stop the spam that triggered the reports.
Wait 24-48 hours for the listing to expire.
Monitor to ensure no new reports are filed.

SORBS Removal#

Check your listing: Use the SORBS lookup tool to identify which specific list you are on.
Fix the issue: SORBS listings require the underlying problem to be resolved.
Submit a delisting request: SORBS provides a web-based delisting form. Some lists (like the DUHL for dynamic IPs) require contacting your ISP.
Processing time: SORBS can take several days to process delisting requests.

SpamRATS Removal#

SpamRATS listings in the RATS-Dyna and RATS-NoPtr categories often indicate DNS configuration issues:

RATS-NoPtr: Set up proper reverse DNS (PTR record) for your sending IP. Once the PTR record is in place, submit a delisting request through the SpamRATS website.
RATS-Dyna: Contact your ISP to have your IP reclassified from dynamic to static.
RATS-Spam: Resolve the spam issue and request delisting.

Prevention Strategies#

Removing yourself from a blacklist is reactive. Prevention keeps you off blacklists in the first place.

Configure SPF, DKIM, and DMARC#

These three DNS records form the foundation of email authentication:

SPF: Specifies which IP addresses are authorized to send email for your domain.
DKIM: Adds a cryptographic signature to your outbound emails, verifying they have not been tampered with.
DMARC: Tells receiving servers what to do when SPF or DKIM checks fail (quarantine, reject, or report).

A properly configured SPF record with -all (hard fail), active DKIM signing, and a DMARC policy of quarantine or reject signals to blacklist operators and receiving servers that you take email security seriously.

Use the Nova Uptime Email Health Checker to verify that all three records are correctly configured and identify any weaknesses.

Maintain List Hygiene#

Remove hard bounces immediately. Continuing to send to addresses that bounce indicates poor list management.
Process unsubscribe requests within 24 hours.
Never purchase email lists.
Use double opt-in for new subscribers.
Remove subscribers who have not opened or clicked in 6-12 months.

Monitor Sending Volume and Patterns#

Sudden spikes in email volume trigger blacklist algorithms. If you need to increase your sending volume, ramp up gradually over several weeks. Consistent sending patterns are less likely to be flagged.

Secure Your Infrastructure#

Keep all server software updated.
Use strong passwords and two-factor authentication for email accounts.
Close open relays and open proxies.
Monitor your outbound email queue for unusual activity.
If you are on shared hosting, consider a dedicated IP for email sending.

Set Up Ongoing Monitoring#

A one-time blacklist check is not enough. Blacklisting can happen at any time due to factors outside your control (a compromised account, a new IP reputation issue, or a spam trap hit). Setting up continuous monitoring with Nova Uptime ensures you are alerted as soon as a blacklist issue is detected, giving you time to act before it impacts your business.

Nova Uptime's email health monitoring checks blacklist status on a configurable schedule (default: weekly) for every domain you monitor. If your score drops or a new blacklist listing is detected, you receive an alert with the specific details you need to start the removal process.

How Blacklisting Impacts Your Business#

The consequences of blacklisting extend beyond just email deliverability:

Missed invoices and payment confirmations: Customers do not receive receipts or invoices, causing support volume to spike.
Failed password resets: Users cannot reset their passwords, effectively locking them out of your service.
Marketing campaign waste: Email campaigns sent during a blacklisting period have significantly lower reach.
Customer churn: If customers cannot receive your emails reliably, they lose trust and move to competitors.
Domain reputation damage: Blacklisting contributes to a long-term domain reputation score. Even after delisting, the historical data remains and can affect future deliverability.

How to Check the Barracuda Blacklist (BRBL)#

The Barracuda Reputation Block List is one of the most commonly queried blacklists. Thousands of organizations use Barracuda email security appliances, so being listed on BRBL has significant deliverability impact.

Check Your IP on Barracuda#

Go to Barracuda's lookup page at barracudacentral.org/lookups
Enter your mail server IP address (find it from your MX record — use Nova Uptime's free Email Health Checker to identify your MX servers)
The tool returns "Listed" or "Not Listed" status

You can also check programmatically by querying the DNS blacklist zone b.barracudacentral.org. If your IP is 1.2.3.4, query 4.3.2.1.b.barracudacentral.org — a positive response means you are listed.

Barracuda Delisting Process#

Fix the root cause — Barracuda lists IPs for sending spam, having poor sending practices, or hosting compromised accounts
Submit a removal request at barracudacentral.org/lookups/lookup-reputation
Provide your IP address and a brief explanation of what caused the listing and what you fixed
Barracuda typically processes removal requests within 12-24 hours
Monitor after delisting — if the underlying issue is not resolved, Barracuda will relist the IP quickly

Why Barracuda Listings Happen#

Sending bulk email without proper authentication (SPF, DKIM, DMARC)
Shared hosting IP where another tenant sends spam
Compromised email accounts sending spam without your knowledge
Sudden volume spikes that trigger Barracuda's automated detection

Use Nova Uptime's Blacklist Checker to monitor your IP across 60+ blacklists including Barracuda, Spamhaus, SpamCop, and SORBS — all in one check.

Frequently Asked Questions#

Is my email blacklisted?#

The fastest way to check is to run your domain through a free blacklist checker. It queries your mail server IPs against 60+ DNS blacklists simultaneously. You can also check your full email authentication status with the Email Health Checker, which includes blacklist checks alongside SPF, DKIM, and DMARC validation.

How do I check if my Gmail is blacklisted?#

Gmail uses Google's infrastructure, so individual Gmail addresses are not typically blacklisted. However, if you send email through a custom domain (e.g., you@yourdomain.com via Gmail/Google Workspace), your domain's sending IP can be blacklisted. Check your domain with a blacklist checker to see if any of your MX server IPs appear on blacklists.

How long does blacklist removal take?#

It depends on the blacklist. SpamCop listings expire automatically in 24-48 hours. Barracuda processes removal requests in 12-24 hours. Spamhaus SBL removals can take 1-7 days. Some blacklists like UCEPROTECT Level 3 can take weeks. The key is to fix the root cause first — requesting removal without fixing the problem leads to immediate relisting.

Can I prevent being blacklisted?#

Yes. Set up proper email authentication (SPF, DKIM, DMARC), maintain clean mailing lists, monitor your sending reputation, and use dedicated IP addresses for important email. Nova Uptime monitors your blacklist status on a schedule and alerts you immediately when a listing is detected.

What is a DNSBL / DNS blacklist?#

A DNSBL (DNS-based Blackhole List) is a database of IP addresses published via DNS. Email servers query these lists in real time when receiving incoming mail. If the sending IP appears on the list, the email may be rejected or filtered to spam. Major DNSBLs include Spamhaus, Barracuda BRBL, SpamCop, and SORBS.

Conclusion#

Email blacklists are a necessary part of the email ecosystem, but they can catch legitimate senders who have configuration issues, inherited bad IP reputation, or fallen victim to compromised accounts.

The approach is straightforward: check your status regularly, fix any underlying issues immediately, follow the correct removal procedures for each blacklist, and put prevention measures in place to avoid relisting.

Start by running a free check with Nova Uptime's Email Health Checker to see your current blacklist status alongside your SPF, DKIM, and DMARC configuration. If you need ongoing monitoring, Nova Uptime checks your email health on a configurable schedule and alerts you when issues arise.

Is My Email Blacklisted? — Quick guide to checking and fixing blacklist issues
Check Barracuda Blacklist (BRBL) — Barracuda-specific checking and removal
SPF Record Setup & Check Guide — Prevent blacklisting with proper SPF
DKIM Check & Setup Guide — Set up DKIM authentication
DMARC Test & Configuration Guide — Enforce DMARC for full protection
Free Blacklist Checker — Check your IP against 60+ blacklists instantly