IP Blacklist Checker

The IP Blacklist Checker tests any IP address against 20+ major DNSBL (DNS-based blacklists) commonly used by mail servers to reject spam. Being listed on even one popular blocklist — Spamhaus SBL/XBL, Barracuda, SORBS, SpamCop, UCEPROTECT — can severely damage your outbound email deliverability, cause message rejections at receiving MTAs, and hurt your sender reputation across the ecosystem.

Mail server operators, deliverability engineers, ISPs, cloud providers and SOC analysts run blacklist checks constantly. New cloud IPs frequently arrive already listed because a previous tenant sent spam. Compromised web servers can end up listed within hours of being turned into a spam relay. Even a single spammy campaign from a shared IP can trigger a listing that takes days to clear.

Once you spot a listing, follow each blocklist operator's delisting process — most have a public webform, some require you to prove the underlying issue is fixed, and a few (like UCEPROTECT) automatically expire listings after a set period. Combine this check with our reverse DNS tool to make sure the IP has proper PTR alignment, which is a prerequisite for delisting on many blocklists.