Blacklist (DNSBL) check: is your IP or domain listed?

A DNSBL (DNS-based blocklist) lists IP addresses and domains associated with spam, malware or abuse. A listing on a widely used DNSBL causes many mail servers to silently reject or quarantine your mail, and in severe cases browsers or security software may warn visitors away from a listed domain.

What it will check

• Your current public IP, or a domain you enter, against several major public DNSBLs in one pass.
• Which specific lists it is on, since each has its own cause (spam source, open relay, compromised host, malware C2) and delisting process.
• A direct link and plain-language steps to request delisting from each list it finds.

Why this is not live yet

Querying many DNSBLs reliably needs rate-limited, cached infrastructure shared across every visitor — making a fresh DNS query per DNSBL per visitor does not scale safely and risks tripping the lists’ own abuse protections. It ships with the AdminKit Check API.

Check manually today

A DNSBL lookup is itself just a DNS query: reverse the IP’s octets, append the DNSBL zone, and query for an A record. For example, to check 203.0.113.5 against Spamhaus ZEN:

dig +short 5.113.0.203.zen.spamhaus.org

Any A record in the 127.0.0.x range means a listing (the exact address encodes the reason); no answer means not listed on that zone. Repeat against other DNSBL zones you care about — see Spamhaus’s usage terms for query-volume limits before scripting this against many addresses.