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Free tool
Build the exact DNSBL query for any IPv4 or IPv6 address, see which public blocklist zones cover its address family, and get the delisting route for each. No zone is queried, and no address is reported clean.
Read this before you read a result
Reading your address…
How a DNSBL works
Understanding the mechanism is what lets you check an address in one command and read the answer correctly, whichever tool you use.
A DNS blocklist publishes its listings as A records in a zone. To ask whether 198.51.100.24 is listed, you reverse the octets, append the zone, and resolve the result. If the name resolves, the address is listed; if it returns NXDOMAIN, it is not listed in that zone at that moment.
IPv6 works the same way with a much longer label: the address is expanded to its full 32 hex digits, each digit becomes its own label, and the whole thing is reversed. That is the step people get wrong by hand, and getting it wrong produces a confident "not listed" that means nothing. The tool above builds the label for you.
Coverage is uneven and worth knowing before you rely on a result: 1 of the 7 zones in our registry answer for IPv6 at all. An IPv6 address checked against the other zones is not clean, it is unchecked.
Answers are not a simple yes or no either. The returned address sits in 127.0.0.0/8 and its last octet identifies which sub-list matched, which is the difference between "this range is registered as dynamic end-user space" and "this host was seen relaying abuse an hour ago". The first is normal for a residential address; the second needs fixing before any delisting request will hold.
# IPv4 — reverse the octets, append the zone
dig +short 24.100.51.198.zen.spamhaus.org
# IPv6 — reverse the nibbles, append the zone
dig +short 1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.dnsbl.dronebl.org
# Nothing printed means the zone holds no listing right now.
# An address in 127.0.0.0/8 means listed; the last octet says which list.What a listing means
Treating every listing the same way is why delisting requests get refused. The sub-list that matched tells you what to fix.
The range is registered as consumer space that should not be delivering mail directly. For a residential proxy address this is expected and usually harmless for web traffic. It is not a reputation problem and there is normally nothing to fix.
Something on the address was seen behaving like a bot or an open relay. This one matters: the underlying cause has to be resolved before removal, and a delisting granted while the behaviour continues will be reversed within hours.
The address sent to a trap. Stop the sending, work out how the trap address entered the list, and only then request removal. Repeat listings after a delisting are treated far less generously than the first.
The address is listed because a neighbour was, and the operator escalated to the whole range. There is often nothing you can do directly — the network owner has to act — which is a strong argument for buying from a provider that polices its own pool.
Netblock escalation is the reason pool hygiene is a purchasing criterion rather than a marketing line. We sell 2 datacenter-backed products and replace flagged addresses rather than leaving a customer on a range that a neighbour has already burned. The residential vs datacenter proxies comparison sets out where each pool type sits on this.
How to use it
Paste the IPv4 or IPv6 address to check, or leave the field empty to use the address your request arrived from.
Confirm the address is routable unicast rather than reserved space, and check how many zones cover its address family.
Each row carries the exact DNS name for that zone: reversed octets for IPv4, reversed nibbles for IPv6, with the zone appended.
An answer inside 127.0.0.0/8 means listed; the final octet identifies the sub-list. Follow the operator's delisting route only after the cause is fixed.
Questions
Related: IP address lookup for what an address discloses, and the proxy tester for latency and the exit address of an endpoint.
Flagged addresses are replaced rather than reassigned, residential exits are sourced with consent, and every plan can target country, city and ASN so you are not sharing a range with whoever bought it last week.
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