Blacklist Checker
Check whether an IP address or domain is listed on the DNS blocklists that mail receivers actually consult.
What a blacklist listing actually does to you
SPF, DKIM and DMARC answer the question "is this message really from you?". A blocklist answers a blunter one: "should we accept anything from this machine at all?" The second question is asked first, and a bad answer ends the conversation before authentication is ever considered.
That is why a domain with flawless SPF, DKIM and DMARC can still see its mail vanish. If the sending IP is on a list the receiver consults, the message is refused at the door.
Not all lists carry the same weight
Tools that advertise "300+ blacklists" are counting padding. A large share of those lists are defunct, unmaintained, or consulted by nobody. SORBS, for years a fixture of every checker, shut down entirely — yet checkers still query it and report a reassuring "not listed", which is true of literally every IP on earth.
We query a curated set instead, and we qualified every one of them empirically: a list only
ships here if it correctly reports the control address 127.0.0.2
as listed and 127.0.0.1
as not listed. Dead lists fail that test. So do lists that quietly refuse our queries.
Each result is labelled by real-world impact. A Barracuda or SpamCop listing will cost you delivered mail today. A UCEPROTECT Level 2 listing usually will not, because it lists entire netblocks — you are frequently there because a stranger on your hosting provider's network sent spam.
A refused query is not a clean result
Several blocklists answer queries that arrive via public DNS resolvers with a sentinel code in
127.255.255.0/24
meaning "refused". Others use
127.0.0.1
to mean "refused", and at least one uses that same code to mean whitelisted.
A checker that assumes "any 127.x answer means listed" will therefore tell you that you are blacklisted when you are not — on every lookup, including for addresses that cannot be listed at all. We decode those codes and report the list as unchecked, excluded from the total. An unknown is never counted as a pass.
If you are listed
- Find the cause before requesting delisting. Delist a still-spamming IP and you are relisted within days, often with a longer cooldown.
- Check the usual suspects: a compromised mailbox, an open relay, a contact form with no rate limit, or a purchased list generating complaints.
- Clean the list you send to. Hard bounces and spam traps are what put you on these lists. Verifying a list before you mail it is the single most effective prevention.
- Then request removal using the link shown beside each listing.
Step three is the one people skip. Most listings trace back to mailing an unverified list: the dead addresses bounce, the spam traps report you, and your reputation collapses. The Mailvalid API removes those addresses before you send, and you can start with 100 free credits.
Frequently asked questions
What is an email blacklist?
A blacklist, or DNSBL, is a published list of IP addresses and domains known to send spam. Receiving mail servers query these lists in real time, before accepting a message. If your sending IP is listed on a major one, a large share of your mail is rejected or filed as spam no matter how well your SPF, DKIM and DMARC are configured.
Why do you not check Spamhaus?
Because doing so honestly requires a licensed key. Spamhaus refuses queries that arrive through public DNS resolvers, answering with a code in the 127.255.255.0/24 range rather than a real result — a checker that misreads that as a listing will tell every visitor they are blacklisted. Its free tier also does not permit a public query service. Rather than show you a fabricated Spamhaus result, we omit it and say so. Check Spamhaus directly at check.spamhaus.org.
I entered a domain. Which IP did you actually check?
A domain's sending IP cannot be discovered from DNS — nothing publishes it. The closest public proxies are the IPs the domain resolves to (its A records) and the IPs behind its mail servers (its MX records), so those are what we check, and we show you each one. If you send through an ESP, your actual sending IPs belong to them and will not appear here; check the IP shown in a message's Received: headers instead.
I am listed. How do I get removed?
Fix the cause first, or you will be relisted within days. Common causes are a compromised mailbox sending spam, an open relay, a misconfigured web form, or a purchased mailing list generating spam complaints. Once the source is fixed, use the delisting link we show next to each listing. Most lists remove a clean IP within hours; some, like UCEPROTECT, remove automatically after a quiet period.
Why do some lists show as 'refused' rather than listed or clean?
Some blocklists rate-limit queries or decline them entirely when they arrive through a public resolver. When that happens we report the list as unchecked rather than guessing. It is not a clean result for that list, and we do not count it toward the total. Reporting an unknown as a pass is how checkers end up giving false reassurance.
Does being on one blacklist matter?
It depends entirely on which. A listing on Barracuda, SpamCop or Spamhaus has immediate, measurable delivery impact because large receivers consult them. A listing on UCEPROTECT Level 2 or 3 usually does not, because those list whole netblocks — often you are there because a stranger sharing your hosting provider's IP range sent spam. We label each listing by impact for that reason.
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Need to verify a whole list?
This tool stops at DNS. The Mailvalid API confirms whether an individual mailbox actually exists over SMTP — in bulk, with 95%+ accuracy. Start with 100 free credits, no credit card.