Check whether an IP address (or a domain, which we'll resolve to its IP) is listed on common spam blocklists - useful if your emails are landing in spam or a mail server is rejecting your connections.
A DNS-based Blackhole List (DNSBL) is a shared list of IP addresses reported for sending spam or exhibiting other abusive behavior. Mail servers commonly check incoming connections against these lists before deciding whether to accept mail - a listed IP can mean legitimate emails silently land in spam or get rejected outright.
Spamhaus operates one of the most widely used blocklists, but since 2022-2023 it has blocked queries from major public DNS resolvers (including the ones this tool has to use) to push high-volume users toward its paid data feed. Querying it through a blocked resolver returns an incorrect "not listed" result rather than a real answer, so we've left it out rather than show you something misleading. If you specifically need Spamhaus's list, use their own official checker.
Most blocklists explain the reason for a listing and how to request removal on their own site - each result below links to it. Common causes include a compromised mail server sending spam without your knowledge, being assigned an IP previously used by a spammer, or misconfigured mail authentication (SPF/DKIM/DMARC). Delisting is usually free but can take anywhere from a few hours to a few days.
Read more: Why Your Emails Go to Spam: Understanding IP Blacklists.