Tests an IP or a domain's mail servers against public blocklists.
When mail starts bouncing or going to spam with no change on your side, the address you send from may be on a blocklist. Lists are run by volunteers and companies who watch for spam and abuse, and receivers consult them before accepting a message.
Enter an IPv4 address, or a domain to check the addresses of its mail servers. Every list is tested for correct operation before its answer is believed, and lists that are down, that refuse shared resolvers, or that answer everything are shown as not checked, never as clear.
Find out why before asking for removal. A listing that is delisted while the cause (a compromised mailbox, an open relay, a forgotten script) is still sending will return within hours.
Not directly. Providers share addresses between customers. A listing there is theirs to resolve, though it is worth telling them if your mail is affected.
Spamhaus answers only resolvers it has agreed to serve, and not the shared public resolvers this server uses. The result would be a false all-clear, so it is declared as not queryable. Use check.spamhaus.org for it.
The lists we can query reliably cover IPv4. IPv6 reputation is mostly assessed by provider rather than by public list.