IP/Domain Blacklist Checker

Enter the IP address or domain you want to check against multiple blacklists.

About DNS Blacklists

This tool checks if an IP address or domain name appears on various DNS-based blacklists (DNSBLs) and Real-time Blackhole Lists (RBLs). These blacklists are used by email servers and security systems worldwide to identify and block potential sources of spam, malware, and other malicious activities.

What are DNS Blacklists?

DNS Blacklists are databases of IP addresses and domains that have been identified as sources of:

  • Spam or unsolicited bulk email
  • Email containing viruses or malware
  • Phishing attempts
  • Compromised systems (like botnets)
  • Open proxies or relays that can be abused

These lists are published using the Domain Name System, making them easy to query in real-time during email delivery or other online transactions.

How DNS Blacklists Work

When your email server or security system receives a connection, it can perform a DNS lookup against multiple blacklists to check if the sender's IP address or domain is listed:

  1. The system takes the connecting IP address (e.g., 192.0.2.1)
  2. It reverses the IP address (1.2.0.192)
  3. It appends the blacklist's domain (1.2.0.192.zen.spamhaus.org)
  4. It performs a DNS lookup on this constructed domain
  5. If the lookup returns an IP address (usually in the 127.0.0.x range), the IP is listed
  6. Different return codes (like 127.0.0.2, 127.0.0.3) often indicate different listing reasons

For domain-based blacklists, the original domain is directly queried against the blacklist service.

How to Interpret Results

  • Not Listed - The IP/domain does not appear on this blacklist. This is generally good.
  • Listed - The IP/domain appears on this blacklist. This indicates potential problems that may affect email deliverability or reputation.
  • Error - The check couldn't be completed due to timeout, connection issues, or server problems.
  • Skipped - The check was skipped because it wasn't applicable (e.g., a domain-specific blacklist check for an IP input).

Why Being Listed Matters

Being listed on one or more blacklists can have several negative consequences:

  • Email Deliverability Issues - Emails sent from listed IPs/domains may be rejected or marked as spam
  • Reputation Damage - Your domain or hosting reputation can be damaged
  • Reduced Network Performance - Some networks may throttle or block traffic from listed IPs
  • Customer Trust - Legitimate emails not reaching customers can harm business relationships

Common Reasons for Blacklisting

  • Compromised Server or Website - Malware on your server sending spam or hosting malicious content
  • Unsecured Email Server - Open relay or insufficiently authenticated SMTP server
  • Shared IP Reputation - Previous users of your IP address may have engaged in abusive behavior
  • Email Marketing Practices - Sending to purchased lists or not honoring unsubscribe requests
  • Hacked Email Accounts - Compromised accounts sending spam through legitimate mail servers
  • False Positives - Rare but possible incorrect listings

How to Get Delisted

If your IP address or domain appears on a blacklist, you should:

  1. Identify and Fix the Problem - Determine why you were listed and address the root cause
  2. Check Delisting Requirements - Visit the blacklist provider's website to understand their specific delisting process
  3. Submit Delisting Request - Most blacklists have forms or email addresses for delisting requests
  4. Provide Evidence - Demonstrate that you've identified and resolved the issues
  5. Be Patient - Delisting can take anywhere from hours to weeks depending on the blacklist
  6. Monitor Your Status - Regularly check if you remain listed after requesting removal

Common remediation steps include scanning for malware, securing email servers, implementing proper authentication (SPF, DKIM, DMARC), and improving email sending practices.

Frequently Asked Questions

How often should I check blacklists?

If you operate email servers or send bulk emails, it's recommended to check weekly or set up automated monitoring. For regular domains or personal use, monthly checks are usually sufficient.

Does being listed on one blacklist mean I'm on all of them?

No. Each blacklist operates independently with its own criteria and data sources. You might be listed on one but not others.

How long does it take to get delisted?

It varies widely by blacklist. Some may automatically delist after a few days, while others require manual review and can take weeks. Some have specific time penalties (e.g., 30-day listings).

Should I be concerned if I'm listed on just one blacklist?

It depends on which blacklist. Major blacklists like Spamhaus can significantly impact deliverability. Being listed on smaller, less-used blacklists may have minimal impact.

Can I prevent being blacklisted?

Yes, by following email best practices: implement proper authentication (SPF, DKIM, DMARC), maintain clean mailing lists, secure your servers, monitor for compromises, and follow proper IP warming procedures for new sending IPs.

What if I'm using a shared hosting service or shared IP?

If you share an IP with other users and that IP gets blacklisted, you'll need to contact your hosting provider. They typically handle blacklist removal requests for shared infrastructure.

Preventative Measures

To reduce the risk of being blacklisted:

  • Implement Email Authentication - Configure SPF, DKIM, and DMARC for your domains
  • Secure Your Servers - Keep software updated, use strong passwords, and implement proper security measures
  • Monitor Sending Patterns - Watch for unexpected increases in email volume that could indicate compromise
  • Follow Email Best Practices - Use confirmed opt-in for mailing lists and honor unsubscribe requests promptly
  • Regular Security Audits - Periodically scan your systems for vulnerabilities and malware