DNSBL Blacklist Checker - Check IP Reputation Online
DNSBL Blacklist Checker
Check an IP Against Major Public Spam Blocklists
Ready to Check
Enter an IPv4 address above to check its reputation.
Understanding DNSBLs
Mail Server Reputation
Being listed on a major DNSBL can cause your outbound email to be rejected or spam-filtered by receiving servers.
Hosting IP Checks
Check a newly assigned server IP before deploying a mail-sending application on it.
Troubleshooting
Diagnose why outbound mail is being rejected by checking if your sending IP got blacklisted.
Live DNS Query
Queries each blocklist's live DNS zone in real time — results reflect current listing status.
How DNSBL Lookups Work
A DNSBL publishes its blocklist as a DNS zone: to check an IP, its octets are reversed and queried as a subdomain of the blocklist's zone. If that lookup returns a result, the IP is listed; if it returns NXDOMAIN, the IP is clean on that list. This tool checks three of the most widely used blocklists.
Key Takeaways
- Three Major Blocklists: Checks Spamhaus ZEN, SpamCop, and Barracuda Central in one pass.
- IPv4 Only: DNSBL infrastructure is IPv4-based; IPv6 addresses aren't supported by this lookup method.
- Public IPs Only: Private/internal IP addresses are rejected since blocklists only apply to public-facing addresses.