IP Blacklist Checker

Check if an IP (or a domain's IP) is listed on major DNS blacklists like Spamhaus, Barracuda, and DroneBL.

About IP Blacklist Checking

DNSBLs (DNS-based blocklists) flag IPs that have shown spam or abuse. This tool checks multiple DNSBLs and shows whether an IP is listed, along with any reason codes.

How blacklisting works:

  • DNSBLs publish special DNS zones (e.g., zen.spamhaus.org) containing IPs they consider abusive.
  • An IP is queried in reverse (e.g., 1.2.3.4 → 4.3.2.1.zen.spamhaus.org). A reply in the 127.0.0.x range indicates listing.
  • A TXT record often includes a short reason or policy hint to help with remediation.
  • Each provider has different criteria (spam, malware/botnet traffic, open relays/proxies, compromised hosts).

How to use:

  • Enter an IPv4 address, or a domain to resolve to an IP.
  • We query common DNSBL providers and report listing status, return codes, and TXT reasons when available.

How to get an IP delisted:

  1. Identify which provider(s) list the IP and read their TXT reason and policy.
  2. Fix the root cause: stop spam/abuse, patch or clean malware, close relays/open proxies, enforce SMTP auth and rate limits.
  3. Harden email hygiene: correct rDNS/PTR, SPF, DKIM, and DMARC; avoid risky forwarding and autoresponders.
  4. If the IP is residential/dynamic, use a reputable SMTP relay or provider for outbound mail.
  5. Request delisting on the provider’s removal page and follow any verification steps.
  6. Monitor logs and reputation; propagation can take from minutes to a few days due to caching.

Notes:

  • Some providers rate-limit or require registration; timeouts can occur.
  • 127.0.0.x return codes are provider-specific; check the TXT detail for meaning.
  • Most lists focus on IPv4; IPv6 support varies by provider.

FAQ:

  • Does checking affect reputation? No. This tool performs passive DNS lookups only.
  • Why do providers disagree? Lists have different criteria, data sources, and update cadences.
  • Do DNSBLs list domains? DNSBLs list IPs; some separate URIBLs list domains/URLs. This tool checks IPs.
  • How long does delisting take? Anywhere from minutes to a few days, depending on the provider and DNS cache TTLs.
  • Will changing IP help? Only temporarily if the root cause remains. Fix issues first to avoid relisting.
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