My mail is bouncing. Does a listing here explain it?

Sometimes, but check the bounce message first. It usually names the list and includes a URL. If the bounce names a list we do not query, or an internal reputation system at a large provider, this page will show nothing wrong. Large providers mostly use their own reputation data, not public DNSBLs.

How did my address get listed?

The usual causes are a compromised machine or account sending spam, a misconfigured mail server acting as an open relay, a shared hosting neighbour on the same address, or reassignment of an address whose previous holder was listed. Fix the cause before requesting delisting, or the listing returns.

How long does delisting take?

It depends on the operator. Some lists expire entries automatically after a period without further evidence, typically days. Others process a self-service removal within hours. A list that requires evidence of remediation can take longer. Repeated removal requests without fixing the cause slow the process down.

Should I check my home connection here?

You can, and a policy listing is the likely result. Residential ranges are listed as a class because mail should not come directly from them. That is not a problem unless you are trying to run a mail server at home, which is a configuration most receivers reject regardless of the listing.

Does a blacklist listing affect my web browsing?

No. DNSBLs are used by mail servers to filter incoming mail. Some firewalls and forum software consult reputation lists too, which can produce a block on a website, but that is a separate mechanism. Browsing is not filtered by mail blocklists.

IP Blacklist Check

Ask the main DNS blocklists whether an address is listed, and read the return code, its published meaning, and where to request delisting.

Your address216.73.216.7

Listed on 1 zone

Every zone we asked

9 lists

List	Zone	Result	Reason	Check it yourself
Spamhaus ZEN	zen.spamhaus.org	listed 127.255.255.254	Listed, reason code not documented here	The Spamhaus Project
SpamCop Blocking List	bl.spamcop.net	not listed	—	Cisco Talos / SpamCop
Barracuda Reputation Block List	b.barracudacentral.org	not listed	—	Barracuda Networks
SORBS aggregate zone	dnsbl.sorbs.net	not listed	—	SORBS
UCEPROTECT Level 1	dnsbl-1.uceprotect.net	not listed	—	UCEPROTECT-Network
Passive Spam Block List	psbl.surriel.com	not listed	—	Rik van Riel
blocklist.de	bl.blocklist.de	not listed	—	blocklist.de
GBUdb Truncate	truncate.gbudb.net	not listed	—	Message Sniffer / ARM Research Labs
s5h.net RBL	all.s5h.net	not listed	—	s5h.net

Every result comes from the list operator named in the row, queried over DNS. We do not run a blocklist of our own, we do not cache a verdict for more than an hour, and only the operator can delist an address. Delisting links go to the operator's own page.

Terms each operator sets

Read before you automate

Spamhaus ZENFree public mirrors are for low-volume, non-commercial use. Production traffic needs a Spamhaus DQS key.
SpamCop Blocking ListOperated by Cisco Talos / SpamCop.
Barracuda Reputation Block ListRequires free registration of the querying resolver IP with Barracuda.
SORBS aggregate zoneOperated by SORBS.
UCEPROTECT Level 1Level 1 lists single IPs only. Levels 2 and 3 list whole networks and are not queried here.
Passive Spam Block ListOperated by Rik van Riel.
blocklist.deOperated by blocklist.de.
GBUdb TruncateOperated by Message Sniffer / ARM Research Labs.
s5h.net RBLOperated by s5h.net.

Same answer as JSON: /api/v1/blacklist/216.73.216.7

How a DNSBL query works

A blocklist publishes its data in DNS. To check 203.0.113.45 against example-list.org, you reverse the octets and query 45.113.0.203.example-list.org for an A record. NXDOMAIN means not listed. An answer in 127.0.0.0/8 means listed, and the last octet carries the reason. A matching TXT record usually carries a human-readable explanation and a link.

That design is why a check costs one DNS query and why mail servers can afford to run several per message.

Which lists we query

We query a curated set of established, attributed lists and name each one in the result along with a link to its own lookup page. We do not query aggregate mirrors that combine many lists behind one hostname, because those hide which operator actually listed the address, and the delisting process differs per operator.

Lists come and go, and a dead list that answers every query as listed has caused real outages in the past. We remove lists that stop being maintained.

What a clean result does not prove

Nothing here reflects the internal reputation systems at Gmail, Outlook, or Yahoo, which handle a large share of the world’s mail and publish no lookup interface. A clean DNSBL result with mail still going to spam at those providers points at authentication, content, or sending-history problems instead. Check SPF, DKIM, and DMARC with /mx-lookup and read the authentication results in a delivered message with /email-headers.

About this tool

Mail servers check public blocklists before they accept a message. This page queries a curated set of DNS blocklists in parallel with a three second timeout each, and shows listed or not listed per list, the return code the list published, what that code means in the operator's own documentation, and a link to their delisting page. Every list is named and attributed, and results cache for one hour.

How to read the result

Not listed: The list returned NXDOMAIN for the reversed-address query, so no listing exists there at this moment. Listings are point-in-time, and a clean result says nothing about the past.
Listed, with a return code: The list answered with an A record in 127.0.0.0/8, and the final octet is the reason code that each list defines for itself. 127.0.0.2 is commonly a direct spam source, while higher values mean policy, dynamic address space, or proxy detections, and we show what the operator says the code means.
Policy listing versus spam listing: A policy listing means the address sits in a range the operator says should never send mail directly, such as dynamic residential space. It is not an accusation of spam, and it usually cannot be lifted for one address, because the listing describes the whole range.
Timeout or error: The list did not answer within three seconds, or returned a non-standard result. Public mirrors of some lists rate-limit queries from cloud address space, which is where our edge sits, so a timeout reflects our query path rather than the address you checked.
Delisting link: A link to the operator that runs the list, where you can ask to be removed. Some lists drop entries automatically after a quiet period, some need a form, and some want the underlying problem fixed first.

Questions people ask

My mail is bouncing. Does a listing here explain it?: Sometimes, but check the bounce message first. It usually names the list and includes a URL. If the bounce names a list we do not query, or an internal reputation system at a large provider, this page will show nothing wrong. Large providers mostly use their own reputation data, not public DNSBLs.
How did my address get listed?: The usual causes are a compromised machine or account sending spam, a misconfigured mail server acting as an open relay, a shared hosting neighbour on the same address, or reassignment of an address whose previous holder was listed. Fix the cause before requesting delisting, or the listing returns.
How long does delisting take?: It depends on the operator. Some lists expire entries automatically after a period without further evidence, typically days. Others process a self-service removal within hours. A list that requires evidence of remediation can take longer. Repeated removal requests without fixing the cause slow the process down.
Should I check my home connection here?: You can, and a policy listing is the likely result. Residential ranges are listed as a class because mail should not come directly from them. That is not a problem unless you are trying to run a mail server at home, which is a configuration most receivers reject regardless of the listing.
Does a blacklist listing affect my web browsing?: No. DNSBLs are used by mail servers to filter incoming mail. Some firewalls and forum software consult reputation lists too, which can produce a block on a website, but that is a separate mechanism. Browsing is not filtered by mail blocklists.

Last reviewed 2026-09-05.