DNS Blacklist Checker
Check if a domain or IP address is listed on 9 major DNS-based blacklists including Spamhaus ZEN, Barracuda BRBL, SORBS, and SpamCop. Enter any domain name or IP address and instantly see which blacklists have flagged it - with detailed return code explanations and listing reasons. All checks run via DNS-over-HTTPS directly in your browser. Fully private, 100% free, and no signup required.
Check if a domain or IP address is listed on DNS-based blacklists.
Queries 9 blacklists via DNS-over-HTTPS - Spamhaus, Barracuda, SORBS, SpamCop, UCEPROTECT, NJABL, JustSpam, IX.DNSBL, and AHBL.
Why Use Our DNS Blacklist Checker?
Check Against 9 Major DNS Blacklists
The DNS blacklist checker queries Spamhaus ZEN, Barracuda, SORBS, SpamCop, UCEPROTECT, NJABL, JustSpam, IX.DNSBL, and AHBL simultaneously. Get a comprehensive view of whether your domain or IP is listed on the internet's most trusted email reputation databases.
Domain & IP Blacklist Checking
Enter either a domain name or an IP address. If you enter a domain, the DNS blacklist checker automatically resolves it to its IP address(es) and checks each one against all blacklists - saving you the trouble of looking up IPs manually.
Instant Results via DNS-over-HTTPS
All blacklist checks are performed in real-time using DNS-over-HTTPS (DoH) queries directly from your browser. No server-side API, no waiting for batch processing - results appear in seconds with detailed return code explanations for each listing.
100% Private & Free
The DNS blacklist checker runs entirely in your browser. Your domains and IPs are never sent to any intermediary server, stored in any database, or logged. Completely free with no signup, no usage limits, and no premium features.
Common Use Cases for DNS Blacklist Checker
Email Deliverability Troubleshooting
If your emails are landing in spam folders, use the DNS blacklist checker to see if your sending IP is listed on Spamhaus, Barracuda, or SORBS. A blacklist listing is a common cause of email delivery failures that can be resolved once identified.
New Server & IP Reputation Check
Before using a new IP address for email sending or hosting, check its reputation using the DNS blacklist checker. Many cloud and VPS providers issue recycled IPs that may have inherited poor reputation from previous owners.
Domain Acquisition Due Diligence
When purchasing a domain name, check if it has been blacklisted by running it through the DNS blacklist checker. A history of spam or abuse associated with the domain can affect email deliverability and search rankings.
Security Incident Investigation
If you suspect your server has been compromised or used for spam, check its IP immediately with the DNS blacklist checker to confirm whether it has been flagged. Early detection helps limit reputation damage.
ISP & Hosting Provider Monitoring
IT administrators can use the DNS blacklist checker to proactively monitor their organization's IP ranges for blacklist status. Setting up regular checks helps catch issues before they impact email delivery.
Shared Hosting Troubleshooting
On shared hosting, your IP is shared with other websites. If a neighboring site engages in spam, your email delivery may be affected. Use the DNS blacklist checker to determine if your shared IP address has been blacklisted.
Understanding DNS Blacklists
What is a DNS Blacklist?
A DNS blacklist(also called DNSBL or blocklist) is a real-time database of IP addresses known to send spam, host malware, or engage in other abusive network activities. Email servers around the world query these lists when receiving incoming mail - if the sending server's IP appears on a blacklist, the email may be rejected, flagged as spam, or subject to stricter filtering. The DNS blacklist checker lets you query these same databases to see if your own domains or IPs are listed.
How DNS Blacklist Checking Works
- Input resolution: If you enter a domain name, the DNS blacklist checker resolves it to its IP address(es) using DNS-over-HTTPS. If you enter an IP address directly, it skips this step.
- Reverse IP lookup: For each IP, the tool reverses the octets (192.0.2.1 becomes 1.2.0.192) and appends the blacklist zone domain (e.g., 1.2.0.192.zen.spamhaus.org).
- DNS query: The tool performs a DNS A-record lookup on the resulting hostname via DoH. If the lookup returns an address in the 127.0.0.0/8 range, the IP is listed. The specific return code (e.g., 127.0.0.2) indicates the type or reason for the listing.
What the Return Codes Mean
When a blacklist check finds a listing, the DNS response includes a return code in the 127.0.0.x range. Each blacklist uses its own codes:
- 127.0.0.2 - Most commonly means listed as a spam source or open relay.
- 127.0.0.3-127.0.0.9 - Typically indicate specific abuse types (open proxy, exploit, policy violation).
- 127.0.0.10-127.0.0.11 - Often indicate policy-based listings like end-user IP ranges that should not send mail directly.
- Specific codes vary by blacklist provider - the DNS blacklist checker shows a human-readable description for each return code.
Privacy & Accuracy Notes
All blacklist checks are performed directly from your browser via DNS-over-HTTPS to Cloudflare and Google DNS resolvers. Your queries are encrypted in transit, and no data is stored, logged, or transmitted through any intermediary server. Note that DNS blacklists are maintained by independent organizations with different listing criteria - being listed on one blacklist does not necessarily mean you are listed on others, and removal processes vary by provider. Always visit the blacklist provider's website for delisting instructions if you believe an IP has been incorrectly or unfairly listed.
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DNSSEC Checker
Verify if a domain has DNSSEC enabled with proper DS record and RRSIG chain validation for DNS security and authenticity.
SPF Record Checker
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Frequently Asked Questions About DNS Blacklist Checker
A DNS blacklist checker is a tool that queries DNS-based blacklists (DNSBLs) to determine if a domain or IP address has been listed for sending spam, hosting malware, or engaging in other abusive activities. It works by performing DNS lookups against blacklist zones - if the DNS response returns an address in the 127.0.0.0/8 range, the IP is listed. Our DNS blacklist checker queries 9 major blacklists simultaneously and provides detailed return code explanations for each listing.
An IP address can be blacklisted for several reasons: sending unsolicited bulk email (spam), operating an open mail relay or open proxy, hosting malware or phishing sites, being part of a compromised device botnet, or being dynamically assigned to a residential IP range that should not send email directly. Domains can be blacklisted if their IP addresses are listed or if they have a history of spam-related activity. Most blacklists automatically delist IPs once the abusive activity stops, though the timeframe varies by provider.
Yes. The DNS blacklist checker runs entirely in your browser. Your domain names and IP addresses are never sent to any intermediary server, stored in any database, or logged. All queries are made directly from your browser to public DNS-over-HTTPS resolvers (Cloudflare and Google) using encrypted HTTPS connections. The tool is 100% client-side - no backend API exists.
The DNS blacklist checker queries 9 major DNSBLs: Spamhaus ZEN (the most widely used), Barracuda BRBL, SORBS, SpamCop, UCEPROTECT Level 1, NJABL, JustSpam, IX.DNSBL, and AHBL. If you enter a domain name, the tool first resolves it to all associated IP addresses and checks each IP against all 9 blacklists, providing a comprehensive reputation assessment.
DNS blacklists use loopback addresses (127.0.0.x) as return codes to indicate the reason for listing. 127.0.0.2 typically means listed as a spam source. 127.0.0.4-127.0.0.8 often indicate specific types of abuse like open proxies or exploit activity. 127.0.0.10-127.0.0.11 frequently mean policy-based listings. The DNS blacklist checker displays a human-readable description for each return code based on the specific blacklist provider's documented codes.
Removal procedures vary by blacklist provider. Most offer a self-service delisting page on their website where you can request removal - visit the provider's website listed in the DNS blacklist checker results. Before requesting removal, ensure you have stopped the activity that caused the listing (fixed open relays, removed malware, stopped spam). Some blacklists automatically delist after the abusive activity ceases for a period of time.
Yes, our DNS blacklist checker is 100% free to use with no signup required, no usage limits, and no hidden charges. Check as many domains and IP addresses as you need - there are no restrictions on the number of lookups you can perform. No registration, no API keys, and no premium features.
Yes. The DNS blacklist checker accepts both domain names (example.com) and IP addresses (192.0.2.1). If you enter an IP address, it checks that IP directly against all blacklists without the domain resolution step. This is useful when you already know the IP address you want to investigate, such as your mail server's public IP.