How to Check if Your Domain or IP is Blacklisted

One day your emails are flowing smoothly. The next, messages start bouncing or disappearing into spam folders. The culprit is often a blacklisting — your domain or IP address has been added to one or more DNS-based blacklists (DNSBLs) that email servers consult when deciding whether to accept incoming mail.

This guide explains what blacklists are, why you might end up on one, how to check your status using our Blacklist Test tool, and what steps to take to get removed.

What Are DNS-Based Blacklists?

A DNS-based blacklist (DNSBL), sometimes called a Real-time Blackhole List (RBL), is a database of IP addresses and domains that have been identified as sources of spam, malware, or other abusive behavior. Mail servers query these blacklists during the SMTP conversation to decide whether to accept, reject, or flag an incoming message.

The system works using DNS itself. When a mail server receives a connection from IP address 192.0.2.1, it constructs a reverse-format query like 1.2.0.192.dnsbl.example.com and performs a DNS lookup. If the blacklist has an A record for that query, the IP is listed. The specific IP returned (e.g., 127.0.0.2 vs. 127.0.0.4) often indicates the reason for listing.

Major blacklists include:

• Spamhaus ZEN – One of the most widely used blacklists, combining the SBL (known spammers), XBL (exploited hosts), PBL (dynamic IP ranges), and CSS (snowshoe spam) lists.
• Barracuda BRBL – Maintained by Barracuda Networks, widely used by organizations running Barracuda email security appliances.
• SpamCop – A complaint-driven blacklist. Users forward spam to SpamCop, which traces the source and lists the offending IP.
• URIBL and SURBL – Domain-based blacklists that check URLs in the message body rather than the sending IP.
• Composite Blocking List (CBL) – Focuses on IPs showing characteristics of compromised hosts (bots, proxies).

Why Domains and IPs Get Blacklisted

Understanding the root causes of blacklisting is essential for both preventing it and resolving it:

Sending Spam (Intentional or Otherwise)

The most obvious cause. If your server sends unsolicited bulk email, blacklists will notice. But it does not have to be intentional — a compromised web form, an exploited contact page, or a badly configured mail relay can turn your server into a spam cannon without your knowledge.

Compromised Server or Account

Attackers frequently compromise web servers, CMS installations (especially outdated WordPress), and individual email accounts to send spam. A single compromised email account with a weak password can generate thousands of spam messages before you notice. Regular server security audits are essential.

Shared IP Reputation

If you are on a shared hosting plan or a shared IP pool with an email service provider, another tenant's behavior can get the shared IP blacklisted, affecting your deliverability too. This is one of the strongest arguments for using a dedicated IP for email sending.

Missing Email Authentication Records

Domains without proper SPF, DKIM, and DMARC records are more likely to be flagged by reputation systems. While missing authentication alone usually does not cause a blacklisting, it makes your domain more vulnerable and reduces your overall sender reputation.

Sending to Spam Traps

Spam traps (also called honeypots) are email addresses that were either never used for real communication or were once valid but have been converted into traps after being abandoned. Sending to these addresses proves that you are either scraping emails, buying lists, or not cleaning your mailing list — all practices that lead to blacklisting.

How to Check Your Blacklist Status

The fastest way to check whether your domain or IP is listed on major blacklists is to use our Blacklist Test tool. It queries dozens of major DNSBLs simultaneously and returns results in seconds.

Here is what to check:

1. Your mail server IP – This is the IP address that appears in the "Received" headers of your outgoing emails. It may differ from your web server IP.
2. Your web server IP – Some blacklists track IPs associated with malware hosting or phishing pages, not just spam.
3. Your domain name – Domain-based blacklists (like URIBL and SURBL) list domains rather than IPs. These check the domain in the message body and headers.

You should also check your DNS records to ensure your PTR (reverse DNS) record is correctly configured. Many mail servers reject email from IPs whose reverse DNS does not match the sending domain. Use our Reverse DNS Lookup tool to verify this.

How to Get Delisted

If you find your IP or domain on a blacklist, do not panic — but do act quickly. The general process is:

1. Identify and Fix the Root Cause

Before requesting delisting, you must fix whatever caused the listing. If you get removed without fixing the problem, you will just get re-listed (often with a longer penalty). Common fixes include:

• Changing passwords for all email accounts and removing compromised accounts
• Updating or patching vulnerable software (CMS, plugins, web applications)
• Closing open relays or fixing misconfigured mail servers
• Cleaning your mailing list by removing bounced addresses and unsubscribed users
• Implementing rate limiting on contact forms and sign-up pages

2. Request Removal from Each Blacklist

Each blacklist has its own delisting process:

• Spamhaus – Visit their lookup page, search for your IP, and follow the removal instructions. Some listings are removed automatically after the abuse stops.
• Barracuda – Use their online removal request form. Typically processed within 12 hours.
• SpamCop – Listings expire automatically within 24–48 hours after the last spam report. There is no manual delisting.
• CBL – Provides a self-service removal page. Lists are often automatically removed after the compromised host is cleaned.

3. Monitor Continuously

After delisting, monitor your status regularly. Run a check with the Blacklist Test tool weekly, or set up automated monitoring through your email service provider.

Preventing Future Blacklisting

Prevention is far easier than remediation. Follow these practices:

• Configure SPF, DKIM, and DMARC – These are non-negotiable. See our complete guide and validate with the SPF Record Test.
• Set up reverse DNS (PTR records) – Your mail server IP should have a PTR record that resolves back to a hostname, and that hostname should resolve forward to the same IP.
• Use double opt-in – For mailing lists, always confirm subscriptions to avoid spam trap hits.
• Monitor bounce rates – A bounce rate above 2% is a warning sign. Above 5% and you are likely headed for a blacklisting.
• Keep software updated – Outdated CMS installations and plugins are the number one vector for server compromises that lead to spam.
• Use dedicated IPs for email – If you send significant volume, invest in a dedicated sending IP so your reputation is entirely in your own hands.
• Review your Whois records – Ensure your domain registration data is current. Some blacklists and filters take registration quality into account.

Impact Beyond Email

While email deliverability is the most common impact of blacklisting, it is not the only one. Some web-based blacklists (like Google Safe Browsing) can cause browsers to display warnings when users visit your site. Search engines may also demote or deindex blacklisted domains. This is why regular monitoring is important even if you do not send email from your domain.

Use a combination of the Blacklist Test, DNS Lookup, and SPF Record Test tools on GF.dev to maintain a comprehensive view of your domain's health and reputation.