Enter an IPv4 address, a domain or an email address and the checker works out which one it is. An IP is checked against more than 20 public email DNS blacklists (DNSBLs) such as SpamCop, Barracuda and UCEPROTECT; a domain, or the domain of an email address, against public domain blacklists such as SURBL. It is free, runs in your browser over DNS-over-HTTPS, needs no signup, and stores nothing.
Create a free Unspam account to save your results and re-run these checks anytime, so you catch a broken setup before it costs you. No credit card.
An email blacklist, also called a DNS blacklist (DNSBL) or RBL, is a published list that mail servers query in real time over DNS while deciding what to do with a message. If something in the message is listed, the receiving server can defer, junk, or reject it. Each operator sets its own listing rules, so being on one list does not mean you are on the others.
There are two kinds, and they judge different things. An IP blacklist judges the server that sent the mail. A domain blacklist judges the domains that appear inside the message: the links in the body and the sender domain. A clean sending IP does not protect you if a linked domain is listed, and a clean domain does not help mail sent from a listed IP, so a full check covers both.
There is no blacklist for a single mailbox. When you enter an email address, the checker takes the part after the @ and checks that domain, so the result applies to every address on it.
An IPv4 address such as 203.0.113.10 runs the IP check, with a reverse DNS (PTR) check alongside. A domain such as example.com, or an address such as you@example.com, runs the domain check, with the domain's public registration data and the reverse DNS of its mail servers. The result card names which check ran. IPv6 addresses are not supported.
A blacklist answers each query with an address in the 127.0.0.0/8 range when the IP or domain is listed, and with no record when it is clean. Which code means what is set by each list, not by a shared rule, so every answer is read against the code table of the list that sent it, and a blocked query is shown as 'no answer' rather than as a listing.
Spamhaus blocks lookups sent through public DNS resolvers, and URIBL does the same for domains, so a browser-based check can never get a trustworthy verdict from them. Rather than show a meaningless row, the tool links them below the results so you can check directly at check.spamhaus.org and uribl.com.
Where a list's operator publishes a lookup or removal page, the listed row links to it. Fix the cause before you use it: a removal request filed while the problem is still live is usually rejected, or the listing comes back within hours.
Levels 2 and 3 do not list your specific IP for your own behavior. They flag the wider subnet or the whole network (ASN) because of other senders on it. Raise it with your hosting provider or ESP, who owns the network range.
On a shared sending IP, one bad sender can get the address listed and hurt everyone on it. You usually cannot fix this alone: report it to your email provider or host so they can fix the cause and request delisting.
Domain lists react to the domains seen inside messages, often because spammers link to your domain or because a hacked site is serving spam pages. Find and fix the cause, then file the removal request with the list that has you.
Blacklists are only one signal. Authentication, engagement, complaint rates and content also decide placement, and a blacklist lookup cannot see any of them. Check SPF, DKIM and DMARC, then test where your mail actually lands.
