About this tool
DNS-based blocklists (DNSBLs, RFC 5782) are lists of IP addresses that their operators consider sources of spam or abuse. Mail servers query them to decide whether to accept a message. If your mail server's IP is listed, some recipients may reject or spam-folder your mail.
For a domain, the tool checks the IPs of its A record and its mail servers (MX). Only lists whose terms allow this kind of public lookup are used — see blocklist sources and terms.
How to read the results
Listed: the list returned an address in 127.0.0.0/8; the return code and any reason text from the list are shown. Not listed: the list answered and has no entry. Check failed: the list did not give a usable answer (timeout, rate-limit or error code) — this is not the same as "not listed".
A listing does not by itself prove malicious activity. Common innocent causes are: shared hosting where another customer sent spam, a residential or dynamic IP range listed by policy, a previous user of the same IP, or a compromised device on the network. Find and fix the cause, then use the list's removal page.
Limitations
- Only the listed free/permitted blocklists are checked. Large mailbox providers (Gmail, Microsoft, Yahoo) use private reputation data that no public tool can see.
- Spamhaus, Barracuda, SpamRATS and Abusix require a key, registration or commercial licence and are off unless the site operator configures them.
- Most of these lists cover IPv4 only; IPv6 support is marked per list. Domain-based (URI) blocklists are not used because their terms require paid agreements for this use.
- For domains, at most four addresses are checked per request to keep query volumes low.
Frequently asked questions
My IP is listed. What should I do?
First find the cause: check for compromised accounts or devices, open relays, or a web form sending spam. Then follow the removal link for that list. Many lists expire entries automatically once the activity stops.
Why is my home IP listed?
Some lists include residential and dynamic IP ranges by policy, because home connections should send mail through a provider's mail server, not directly. This is not an accusation of abuse.
Why don't you check Spamhaus?
Spamhaus requires a key for queries from hosting networks, and its free tier is for non-commercial use only. It can be enabled by the site operator with a licence. You can check Spamhaus directly on its own website.
How current are the results?
Each row shows the time it was checked. Results are cached for up to 15 minutes to protect the list operators from repeated queries.
Is being blacklisted permanent?
Usually not; many lists remove entries once abuse stops.
Does a listing mean my server is hacked?
Not necessarily; shared or reused IPs are common causes.
How often should I check?
After sending problems, or regularly if you run a mail server.