IP Blacklist Check
Check any IPv4 address against five live blocklists — Spamhaus ZEN, SpamCop, PSBL, Barracuda and UCEPROTECT — plus reputation, ASN and proxy signals.
# free & rate-limited · no signup · live results from the same engine as the API
Since the engine is the same one the API runs, a key does not buy you a better answer. It buys volume, bulk jobs and a signed receipt.
Three quick steps
Enter an IP
Paste any IPv4 address to review.
Live lookup runs
We check reputation and blocklist status.
Read results
See reputation, risk, and blocklist flags.
Reputation score
A reputation and risk rating for the IP.
Blocklist status
Whether the IP appears on major lists.
Threat signals
Known abuse and threat intelligence.
Connection context
ISP and connection type context.
Who uses it
Email senders
Check sending IP reputation.
Security
Screen inbound connections.
Fraud teams
Flag known-bad IPs.
Developers
Automate reputation checks.
Which blocklists this checks, and what a listing means
This runs a live DNS query against five independent blocklists every time — nothing is read from a stale local copy of somebody's list. Below is exactly which ones, what each operator actually lists, and where to go if you find yourself on one. If a tool will not tell you which lists it queried, its answer is not something you can act on.
| Blocklist | Zone | What it lists | Removal |
|---|---|---|---|
| Spamhaus ZEN | zen.spamhaus.org | Combined feed: known spam sources, hijacked addresses, and ranges that should not send mail directly | check.spamhaus.org |
| SpamCop | bl.spamcop.net | Addresses reported by SpamCop users and spam traps; listings expire automatically once reports stop | spamcop.net/bl.shtml |
| PSBL | psbl.surriel.com | Passive Spam Block List — spamtrap-driven, with automatic expiry and a deliberately low false-positive policy | psbl.org |
| Barracuda | b.barracudacentral.org | Reputation feed built from Barracuda's own mail-flow telemetry | barracudacentral.org/rbl/removal-request |
| UCEPROTECT Level 1 | dnsbl-1.uceprotect.net | Single addresses caught sending to spam traps; Level 1 is the individual-IP tier, not the whole-network ones | uceprotect.net/en/rblcheck.php |
What a listing costs you in practice
The practical effect is on outbound email. Receiving mail servers consult these lists at connection time, so a listed sending IP gets refused, deferred or filed as spam before your message is ever read. If you run your own mail server or a marketing platform on a dedicated IP, a listing shows up as a sudden collapse in delivery rates.
It is not a security score. Plenty of listed addresses belong to ordinary residential connections, shared hosting or mobile networks that were never involved in anything abusive. Blocking users because their IP appears on a list will block real customers.
Getting delisted, in the order that actually works
First find the cause. The usual ones are a compromised mailbox sending on your behalf, an open relay or misconfigured form, a purchased mailing list hitting spam traps, or a neighbour on a shared IP. Delisting before the cause is fixed simply resets the clock.
Then check your sending fundamentals: valid reverse DNS on the sending IP, SPF and DKIM aligned with the domain you send from, and a DMARC record. Several list operators will not process a removal for an IP that has no reverse DNS at all.
Then request removal at the operator's own page — the Removal column above links to each. Lists with automatic expiry, like SpamCop and PSBL, often need no request at all once the traffic stops.
Why five lists and not fifty
Number of lists is a vanity metric. There are hundreds of DNSBLs and many are abandoned, unmaintained, or run on a policy so aggressive that a listing tells you nothing. Some charge for removal, which creates an obvious incentive problem.
We check five that are independently operated, widely consulted by actual receiving mail servers, and free to query and to leave. We removed one from this set on 1 August 2026 when its operator retired it — a dead zone answers nothing while still costing you a DNS round trip, and a tool that keeps querying it is quietly reporting a check it never made.
What this tool does not do
It checks IPv4 addresses, not IPv6 and not domains — domain and URI blocklists are a separate mechanism with different operators. Blocklist status is cached for three days, because listings move on a scale of days and re-querying on every request would be noise, not freshness.
It also does not tell you your sending reputation with any individual mailbox provider. Gmail, Outlook and Yahoo each maintain internal reputation systems that no public list can see; a clean result here means nothing was listed publicly, not that a specific provider is accepting your mail.
FAQ
Is this IP blacklist check tool free?
Yes. Guests get 5 lookups a minute and 50 a day, no signup. A free account has 200 credits a month, no card, and core validations cost 1 credit each.
How accurate are the results?
The free tool runs the same engine as the API, so what you see here is what an integration returns. Where we cannot determine something we say so rather than guessing — a confident wrong answer is worse than an honest gap.
Can I use this in bulk or via API?
Yes. Paste 20 numbers with no account, or sign in and clean 100 a month on the free plan. Paid plans take longer lists, CSV jobs, webhooks and higher rate limits, from $3.16 per 1,000 core lookups.
What is the difference between a blacklist, a blocklist and a DNSBL?
Nothing — they are the same thing under different names. DNSBL (DNS blocklist) and RBL (realtime blackhole list) are the technical terms; blacklist and blocklist are the everyday ones, with blocklist now the preferred wording across the industry. This tool is a blocklist checker regardless of which name you searched for.
How do I verify whether my IP is blacklisted?
Enter it above. We query five independent blocklists live over DNS and show which ones, if any, return a listing. There is nothing to install and no account needed to test an address.
Does a listing mean the IP is malicious?
No, and treating it that way causes false accusations. Most listings mean an address sent mail that landed in spam traps, sits in a range a list operator considers residential or dynamic, or shares a block with something that misbehaved. It is a mail-delivery signal, not a verdict about the person behind the address.
How long does it take to be removed from a blacklist?
It depends on the list. Some expire listings automatically after a quiet period of days to weeks; others require you to request removal and will re-list immediately if the underlying problem is still there. Fix the cause first — an open relay, a compromised account, a bad mailing list — because a delisting request on an unfixed IP buys hours, not a solution.
Do you check IPv6 addresses?
Not currently. The blocklist check is IPv4 only, because most of these lists have limited or no IPv6 coverage and returning "not listed" for an address nobody actually indexed would be misleading.