IP Tools
IP Blacklist Check
Check whether an IPv4 address appears on active spam and abuse blocklists that mail servers use to filter email.
How it works
Each blocklist is published through DNS. To ask a list about 203.0.113.7, the tool reverses the address and looks up 7.113.0.203.<list zone>. No answer means the address isn't listed. An answer starting with 127. means it is, and a TXT record on the same name usually explains why.
Only lists that are still running and free to query are checked. Many older checker sites still show lists that shut down years ago, and some of those now report every address as listed.
FAQ
- What is an IP blacklist (DNSBL)?
- A DNS-based blocklist is a list of IP addresses seen sending spam, infected with malware or otherwise misbehaving. Mail servers check incoming connections against these lists and may reject or flag mail from a listed address.
- My IP is listed. What should I do?
- First find out why: a listed home address often means a device on your network is infected or sending spam, or the address was used by someone else before you. Fix the cause (scan devices, secure your mail server, close open relays), then follow the removal steps on the list's own website. Most lists also remove entries automatically after a quiet period.
- Why does a list show "No answer"?
- Some lists limit or refuse queries from busy shared servers, or are briefly offline. "No answer" means no result came back, not that the address is clean or listed.
- Why don't you check Spamhaus or Barracuda?
- Their free access doesn't cover lookups made on behalf of a public website, so this tool leaves them out. You can check them directly on their own sites.
- Why only IPv4?
- Almost all public blocklists track IPv4 addresses. IPv6 networks are so large that spammers can change address constantly, so lists for IPv6 work differently and are rare.