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DNSBL Checker

A DNSBL, or DNS-based Blocklist, is a list of IP addresses or domains known for sending spam, hosting malware, or other abusive behavior. Mail servers and security tools query these lists during message delivery. A "listed" result usually causes the message to be rejected or scor

Domain Tools
Checks ten major DNS blacklists including Spamhaus ZEN, SpamCop, Barracuda, SORBS.

A DNSBL, or DNS-based Blocklist, is a list of IP addresses or domains known for sending spam, hosting malware, or other abusive behavior. Mail servers and security tools query these lists during message delivery. A "listed" result usually causes the message to be rejected or scor

This free DNSBL Checker from KX Toolkit is part of our all-in-one online toolkit. It runs entirely in your browser, so your data never leaves your device for client-side operations. 100% free, forever - no paywall, no credit card, no trial.

How to use the DNSBL Checker

  1. Enter the domain or IP address.
  2. Pick the record type if the tool supports filtering.
  3. Run the lookup - most checks return in under a second.
  4. Copy the records for your DNS migration or audit notes.

What you can do with the DNSBL Checker

  • Audit DNS before a domain migration.
  • Verify SSL certificate expiry and chain.
  • Check domain age and history before buying.
  • Diagnose email-delivery issues (SPF, DKIM, DMARC).

Why use KX Toolkit's DNSBL Checker

  • Browser-based: Works on Windows, macOS, Linux, iOS and Android - no install, no extension.
  • Privacy-first: Client-side tools never upload your data; server-side tools delete files right after processing.
  • Mobile-friendly: Full feature parity on phones and tablets - not a stripped-down view.
  • Fast: Optimised for instant feedback. No artificial waiting screens, no email-gated downloads.
  • One hub for everything: 300+ tools across SEO, text, image, PDF, code, color, calculators and more - skip switching between sites.

Tips for the best results

DNS changes propagate at different speeds across resolvers - run the same check from Google (8.8.8.8) and Cloudflare (1.1.1.1) before declaring a problem.

Related Domain Tools

If you find this tool useful, explore the full Domain Tools collection or browse our complete tool directory. KX Toolkit is built for marketers, developers, designers, students and anyone who needs a quick utility without signing up for yet another SaaS.

What is a DNSBL and how does it work?
A DNSBL, or DNS-based Blocklist, is a list of IP addresses or domains known for sending spam, hosting malware, or other abusive behavior. Mail servers and security tools query these lists during message delivery. A "listed" result usually causes the message to be rejected or scored as spam. The DNSBL Checker queries dozens of major lists at once and shows which ones flag your IP or domain.
Why is my IP listed even though I do not send spam?
Shared hosting, recycled cloud IPs, and previously compromised servers are common reasons for unjust listings. A new VPS might inherit the reputation of the previous tenant. Some lists are aggressive and include entire ISP ranges. The checker shows which list flagged you and links to the delisting form, where you can request removal after fixing any underlying issue and explaining the situation.
How long does delisting take?
It varies by list. Spamhaus and Barracuda often process requests within hours, while smaller community lists can take days or simply expire entries automatically after a quiet period. The most important step is to fix the cause first, whether that is a compromised account, an open relay, or a reused IP. Submitting repeated delisting requests without resolving the root cause usually results in being relisted.
Do all mail servers use the same blocklists?
No. Each receiver picks its own combination, weighting them differently in spam scores. Being listed on one minor DNSBL might not affect deliverability much, but landing on Spamhaus SBL or Barracuda usually causes immediate problems with major mailbox providers. The checker covers the lists that matter most so you can prioritize remediation by impact rather than chasing every entry equally.
Can listing an IP affect my website too?
Some DNSBLs are also consulted by web application firewalls, content filters, and CDNs to score traffic. A listed IP might face captchas, throttling, or outright blocking when browsing. If your office or VPN IP shows up on a list, employees may struggle to reach common sites. Run the checker against any IP you control to spot reputation problems before they affect productivity or deliverability.
How can I prevent ending up on a blocklist?
Authenticate every outgoing message with SPF, DKIM, and DMARC, monitor bounce and complaint rates, never buy mailing lists, segment newsletters from transactional mail, and patch servers promptly to prevent compromise. For inbound, run anti-virus scanning and rate-limit suspicious senders. Most listings come from a few preventable mistakes, and consistent hygiene keeps your IP's reputation clean for years at a time.

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