Check if your IP address or domain is listed on email blacklists such as Spamhaus, SpamCop, Barracuda and UCEPROTECT. Every result shows which lists answered; a list we could not measure is reported as not checked, never as clean.
Enter an IP address for direct DNSBL lookup, or a domain to check all mail servers
Receiving mail servers look up the connecting IP address in DNS blocklists (DNSBLs) and use the answer to reject or score mail. What a listing does depends on the list and on the receiver:
The check is a plain DNS lookup, the same one a receiving mail server does; no AI is involved. For a domain it takes the IPv4 address of each MX host (the first address per host); for an IP it uses that address. MX hosts are the servers that receive mail for the domain. If you send through another service or relay, your outgoing reputation belongs to that sending IP: enter it here as an IP to check it. It reverses the octets and asks each list for an A record, as RFC 5782 describes: 192.0.2.99 becomes 99.2.0.192.zen.spamhaus.org.
If you are listed: find and fix the cause first (a compromised account or device, an open relay, a form that sends mail for anyone, or bulk mail to addresses that never opted in), then use the removal page of the list that lists you. Many lists expire entries on their own once the traffic stops. A Spamhaus PBL listing is not a spam listing: it marks IP space that should not send mail directly to other servers, such as consumer broadband. Spamhaus allows removal only for an IP that runs a mail server, has matching forward and reverse DNS, and allows outbound port 25 for that server alone (Spamhaus PBL FAQ).
Limits: a domain check covers the receiving MX hosts, which are not necessarily the IPs your mail is sent from. IPv6 addresses are not checked, only the first IPv4 address of each MX host is used, and a list that cannot be measured is reported as not checked rather than clean. A clean result here is not a guarantee of inbox placement; that also depends on SPF, DKIM, DMARC, reverse DNS and content.
Related: guide to checking and delisting, what an email blacklist is, reverse DNS (FCrDNS) check.