Check whether an IP address or domain is listed on major spam blacklists (DNSBLs).
Every other tool on this site runs entirely as JavaScript in your browser and never contacts a server at all. This one is a deliberate exception, by necessity: the IP or domain you enter is sent to this site’s server, which queries several public DNSBL zones on your behalf — unavoidable, since browsers can’t query DNS directly — nothing about the check is logged. Nothing about the request is logged, stored, written to a cookie, or shared with any third party — it's handled and discarded the moment the response is sent back to you.
This describes only what this specific tool does with what you type into it. It doesn't cover the rest of this site — see the Privacy Policy for how analytics and advertising cookies are handled elsewhere.
A DNSBL (DNS-based blackhole list) is a spam-prevention blocklist published as a DNS zone — mail servers and other systems query it before accepting a connection, and a listing can mean your outgoing mail gets rejected or routed straight to spam. This tool checks an IP address against the major IP-based lists (Spamhaus ZEN, Barracuda, SpamCop, SORBS) or a domain against Spamhaus's domain list (DBL), and reports which ones, if any, currently list it.
Being listed doesn't always mean something malicious happened on your end — shared hosting IPs, dynamic residential ranges, and IPs previously used by someone else for spam can end up listed for reasons unrelated to your own activity. If you're troubleshooting bounced or spam-routed email, this is a reasonable first check, but the specific reason code and delisting process differs by list — each operator's own site is the authoritative source for both.
Some DNSBL operators (Barracuda in particular) rate-limit or restrict automated queries from certain server IPs. If a specific list shows as "unavailable" rather than a clear listed/not-listed result, that's most likely this kind of restriction on this server's IP, not a fault with the address you're checking — try that specific list's own site directly for a second opinion.
No — this checks a handful of the most widely used lists, not the full universe of DNSBLs that exist. A clean result here is a good sign, not an absolute guarantee across every list any mail server might consult.
Each list has its own delisting process, usually found on that operator’s own website (search "[list name] delisting"). Fix the underlying cause first — a compromised account, an open relay, or a genuinely abused IP — since delisting without fixing the cause often just leads to being relisted.
Some DNSBL operators (Barracuda especially) rate-limit or restrict automated queries from certain server IPs. That specific list couldn’t be checked reliably from here — it doesn’t mean anything about the address you searched. Try that list’s own site directly.
For email deliverability specifically, the sending server’s IP is usually what matters most — check that with the IP-based lists. A domain-based check (Spamhaus DBL) is more about the domain’s reputation when it appears in message content or links, a related but different concern.