Blacklist Checker Free Tool

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About Blacklist Checker

What This Tool Actually Does

The Blacklist Checker on limitlessreferrals.info answers one narrow question. Is the IPv4 address that hosts a domain's website listed on any of twelve public DNS blacklists? You type a domain name or a bare IP address into the field above, press Submit, and within about five seconds you get a two-part answer. The first part names the domain, shows the single IPv4 address the tool resolved for it, and gives an overall verdict in red or green. The second part is a numbered table with twelve rows, one for each blacklist zone, each marked Listed or Not Listed.

The tool performs its lookups from the server that hosts this page. When you submit a URL, the server takes the host portion, strips the www prefix for display, and performs a plain DNS lookup to obtain the first A record. That address is what gets checked. The domain's mail exchanger, its MX records, and the IP addresses that actually send its email are never queried. People routinely confuse web host reputation with mail reputation, and that confusion produces misleading conclusions about whether a domain is blacklisted.

The twelve zones are queried one after another, never in parallel. For each zone, the tool reverses the IP address into the standard DNSBL query format and asks the zone whether that address appears on its list. An answer that falls inside the 127.0.0.0/8 range, except for the special 127.255.x.x error codes, counts as Listed. Anything else, including no answer at all, counts as Not Listed.

This is a web host reputation check. Mail reputation checks and domain name reputation checks are separate categories of service with separate purposes. The tool's output only tells you what the twelve zones said about one web-facing IPv4 address at one moment in time.

How the Tool Resolves Your Input

The form accepts what it calls a URL, but the processing is forgiving. The input is trimmed, lowercased, stripped of any http:// or https:// prefix, and then validated. If the result is not a valid URL, you see an alert that reads "Alert! Input Site is not valid!". A bare IPv4 address passes validation and is used directly as the host. A domain name like example.com is resolved from the server in Helsinki, Finland, through the public resolvers operated by Cloudflare and Google.

Only the first A record is used. Domains that use round-robin DNS or that sit behind multiple A records may resolve to different addresses on different runs. The tool does not attempt to check all of them. IPv6 is never used, even when the domain advertises AAAA records alongside its A record. This is an IPv4-only tool by design, and the output table makes that explicit by showing the resolved IPv4 address.

The resolution step is where the difference between web host and mail server gets concrete. For a domain that uses Cloudflare's proxy, the A record points to a Cloudflare edge address shared by thousands of unrelated websites. The live test run for this rewrite resolved example.com to 172.66.147.243 and limitlessreferrals.info to 172.67.221.128. Neither of those addresses belongs to the website owner. They belong to Cloudflare's anycast network. If some other website sharing that edge address behaves badly, the shared address can appear on a blacklist, and your domain will show as Listed even though your own content and your own mail server are clean.

The tool never looks at the MX host or the sending IP. A domain can have a spotless web host address and a mail server that is drowning in spam reports. This tool will tell you the web host is clean and stay silent about the mail server. The reverse scenario also happens. A domain's mail server can be listed while its web host address remains untouched, and this tool will report Not Listed because it never asked about the mail server.

The Twelve Blacklist Zones

The tool queries exactly twelve zones, in a fixed order. Each zone has a different operator, a different geographic home, and a different idea of what belongs on a list. Some of them list individual IP addresses. Others list entire provider allocations or whole autonomous systems. Knowing which zone flagged you tells you something about the scale of the problem.

The UCEPROTECT trio deserves a closer look because the three levels behave very differently. Level 1 lists a single IP address when that address has been observed sending spam directly. Level 2 escalates to the provider's entire allocation when the provider ignores abuse reports about a customer. Level 3 escalates further to the whole autonomous system number. A listing at level 2 or level 3 says more about the hosting provider's responsiveness than about the specific website you checked.

DroneBL tracks hosts that have been compromised and used for abuse, including open proxies, SOCKS proxies, and botnet members. SpamCop builds its list from user-submitted spam reports, which means a determined reporter can sometimes get an address listed with thin evidence. Barracuda maintains a reputation system used by its own mail filtering products. blocklist.de focuses on attack traffic, so a compromised server that participates in a distributed denial of service campaign can end up there. The remaining zones, Swinog, JIPPG, Fabel, and JustSpam, are smaller operators with regional followings and their own reporting mechanisms.

Each zone answered the standard test address as Listed in the server-side test run on the day the cleanup happened, all twelve of them. The same test run confirmed that none of the twelve zones flagged example.com, google.com, or limitlessreferrals.info. That combination of results is the expected baseline. The zones respond correctly to a known-listed address and stay quiet for known-clean addresses.

How DNSBL Answers Work

DNS blacklists reuse the domain name system in a specific way. A blacklist zone hosts DNS records that answer queries about IP addresses. To ask whether 192.0.2.1 is listed, a client reverses the octets to 1.2.0.192, appends the zone name, and queries for an A record at that constructed name. If the zone has no information about that address, it responds with NXDOMAIN, meaning the name does not exist. If the address is listed, the zone returns an A record whose address falls in the 127.0.0.0/8 range.

The specific address returned carries meaning. The classic convention maps 127.0.0.2 to a generic listing. Higher values can indicate specific reasons, such as 127.0.0.4 for dialup addresses or 127.0.0.6 for a known spam source. The tool does not decode these reason codes. It treats any answer in the loopback range, except for the special error range starting at 127.255.0.0, as a listing.

The error range is where the old version of this tool went wrong. Some blacklist operators, most notably Spamhaus, refuse to answer queries that arrive through public resolvers. When Spamhaus sees a query coming from a public resolver operated by Cloudflare or Google, it returns the address 127.255.255.254, which is a documented error code meaning "query refused". The old code counted that error code as a listing. Every domain checked through this tool appeared Listed on Spamhaus, even when Spamhaus had no information about the address at all.

A server-side test on the cleanup day confirmed that the twelve zones now in the tool all respond correctly to the standard test address. The test also confirmed that the error-code filter works. The distinction between a real listing answer and a refusal error code is the difference between a useful tool and a permanently false alarm.

Correcting the Old Description of This Tool

The previous version of this page described the tool in ways that did not match its actual behaviour. The old copy claimed the tool queries multiple blacklist databases in parallel. It does not. The twelve zones are queried sequentially, one after another, and the full run takes about five seconds. Parallel queries would finish faster, but the tool was never built that way.

The old copy mentioned a timeout status as a possible outcome. No such status exists in the output. Every zone resolves to exactly one of two states, Listed or Not Listed. A timeout during a query is treated as Not Listed, because the zone failed to provide a listing answer. The user never sees a third state.

The old copy claimed the tool checks the domain name against URIBL and SURBL style lists. Those services, along with Spamhaus DBL, work by looking up the domain name itself. This tool never performs a domain name lookup against any blacklist. It only reverses IP addresses and queries the twelve zones listed above. Domain name blacklists are a separate category of service with a separate purpose.

The old copy named Spamhaus SBL, Barracuda, and SORBS as examples of lists that might flag a domain. Barracuda is still queried, as zone number six. Spamhaus is not queried at all, for reasons the cleanup section explains. SORBS no longer exists. Proofpoint shut it down in June 2024, and no amount of querying will bring it back.

The old copy described the tool as checking the mail-sending IP of the domain. It checks whatever address the domain's A record points to, which is frequently a content delivery network address shared by thousands of sites. The mail server is a separate machine with a separate IP address, and this tool never looks at it.

The old copy mentioned IPv6 support. The tool resolves and checks a single IPv4 address. IPv6 addresses are never queried against any of the twelve zones.

The 2026 Cleanup

On the day the live tests for this rewrite were run, the tool's vendor list was cleaned up. Until that day, the list held twenty-six entries, one of which was a duplicate of bl.spamcop.net. Three of those entries reported every address as Listed. Ten more no longer answered any queries at all.

The three false-positive zones were zen.spamhaus.org, cbl.abuseat.org, and cblplus.anti-spam.org.cn. The Spamhaus and CBL zones failed because of the public resolver problem described earlier. They answered with the 127.255.255.254 error code, and the old code read that as a listing. The cblplus.anti-spam.org.cn zone failed differently. That domain had become a parked wildcard domain, meaning it answered with a real-world address for any name queried, including reversed IP addresses that should have returned NXDOMAIN.

The ten dead zones were a different problem. SORBS was shut down by Proofpoint in June 2024. CBL was folded into Spamhaus XBL back in 2021. The remaining eight, including v4bl, fnrbl.fast.net, dnsbl.anticaptcha.net, singlebl.spamgrouper.com, spam.abuse.ch, virbl.dnsbl.bit.nl, and all.spamrats.com, returned NXDOMAIN or SERVFAIL from this server. Each dead zone cost a timeout before the query failed, which stretched a single check to thirty or thirty-seven seconds and guaranteed an Overall verdict of Listed, because the timeout handling in the old code treated those failures as listings.

The cleanup removed all thirteen problematic entries and added the error-code filter. A check that used to take half a minute and always end in a false positive now takes about five seconds and reports real results. The duplicate SpamCop entry was also removed, bringing the list from twenty-six entries down to the twelve zones that are queried today.

Spamhaus is therefore not checked by this tool. The organization offers a paid Data Query Service for legitimate high-volume users, and it works properly through private resolvers, but the free public resolver path that this tool uses is blocked. Spamhaus runs the most widely used blacklist infrastructure globally, and a clean result from this tool does not cover it. If you need a Spamhaus check, you need a different tool or a direct query from your own mail server.

What the Results Mean

The output page shows a first table with three fields. The Domain field shows the host with its first letter capitalised and the www prefix removed. The Domain IP field shows the resolved IPv4 address. The Overall field shows Listed in red if any of the twelve zones matched, or Not Listed in green if none of them did.

Below that sits the numbered table with one row per zone. Each row shows the zone name and its status, Listed in red or Not Listed in green. The zones appear in the same order every time, starting with the three UCEPROTECT levels and ending with JustSpam.

A full check takes about five seconds. The live tests measured a range of roughly five to six seconds for a complete run. The variation comes from the sequential nature of the queries and the response time of each individual zone. A slow zone can stretch the run, because the tool waits for each zone's answer before moving to the next one.

The live test results were consistent. example.com resolved to 172.66.147.243 and returned Not Listed across all twelve zones, with an overall verdict of Not Listed, in about six seconds. google.com resolved to 142.251.38.78 and returned Not Listed everywhere. limitlessreferrals.info returned Not Listed everywhere. The server-side test address returned Listed on all twelve zones with an overall verdict of Listed, which confirmed that the zones respond correctly to a known-listed address.

Results reflect the moment of the query. Blacklists change constantly. An address that is Listed this minute can be delisted tomorrow, and a clean address can be listed an hour from now after a spam run. The tool gives you a snapshot, not a permanent certificate.

How to Use This Tool

1. Open the tool page. Find the input box above this article, labelled "Enter a URL".
2. Type a domain or IP address. Enter something like example.com, www.example.com, or a bare IPv4 address such as 192.0.2.1.
3. Press the Submit button. The form sends a POST request to the output page, and the server starts resolving the host.
4. Wait about five seconds. The twelve zones are queried one after another, so the run takes a few seconds to complete.
5. Read the first table. Check the Domain IP value first, because that address is what actually got checked.
6. Read the twelve zone rows. Look for any red Listed entries, and note which zone flagged the address.

The tool checks the web host address. If you want to know whether your email is being rejected, you need to check the IP address that your mail server uses for outgoing connections. This tool will not answer that question.

How to Use This Tool for Cloudflare Users

If your domain sits behind Cloudflare's proxy, the Domain IP shown in the results will be a Cloudflare edge address. The live tests showed example.com resolving to one IP address and limitlessreferrals.info resolving to another. Those addresses are shared infrastructure. Thousands of unrelated websites use the same edge addresses, and the reputation of those addresses reflects the behaviour of the entire crowd.

A Listed result on a Cloudflare edge address does not mean your website content is the problem. It means some website sharing that address triggered a blacklist operator's criteria. The path forward is different from the path for a dedicated IP address. You cannot easily change a Cloudflare edge address, and you cannot delist it on behalf of the other sites sharing it.

The practical workaround is to check the origin IP instead. If you know the actual server address behind Cloudflare, you can submit that bare IP address to this tool and get a result that reflects your own hosting. You can find the origin IP by checking your hosting provider's control panel or by disabling the proxy temporarily and resolving the domain again.

The difference between web host and mail server cuts the other way too. If your domain uses Cloudflare for the website but sends email through a separate mail server, the mail server's IP address is what matters to email recipients. This tool never queries the MX host, so it cannot tell you whether your outgoing mail is blacklisted. You would need to resolve your mail server's address separately and check that address.

Limitations

The tool has a set of hard limits that come directly from its code. It checks one address per run, the first A record it finds. It accepts IPv4 only. It checks the web host, never the mail server. It does not query domain name blacklists. It does not query Spamhaus. It does not check Microsoft or Google reputation systems. It shows no listing reason and no listing date. It provides no delisting links.

The sequential query design means a slow zone can stretch the entire run. The server applies its default DNS timeout to each query, and the zones are queried one after another. If one zone stops responding, the tool waits for the timeout before moving on, and the whole check takes longer.

Blacklists are dynamic databases. An address can be listed and delisted within days, and the tool's snapshot only tells you what the zones said at the time of the query.

The rate limiting situation deserves a clear explanation. This tool has no CAPTCHA and no per-tool request cap. A site-wide throttle applies to every page of limitlessreferrals.info. If one visitor address makes more than roughly fifteen requests within a single second, that address is blocked for the rest of the day with a 503 response. For a tool like this one, the check itself makes DNS queries from the server, so each run consumes server resources.

The blacklist operators apply their own limits as well. UCEPROTECT, Barracuda, and SpamCop all restrict how many queries a single resolver can send in a given period. The tool runs from one server in Helsinki, Finland, through the public resolvers operated by Cloudflare and Google, and those resolvers have their own policies about DNSBL traffic.

The Web Host Versus Mail Server Distinction

This distinction is the single most important concept for interpreting the tool's output. A domain name is not a machine. It is a set of DNS records that point to different machines for different purposes. The A record points to the web server. The MX record points to the mail server. Those are often different IP addresses, operated by different companies, in different countries.

Most website owners never think about this separation. They buy hosting from one provider, point the domain at that provider, and assume the whole domain lives on one server. That assumption breaks down for email because email delivery is a separate infrastructure. Many small businesses host their website with one company and their email with another, often because the website host's mail service has a poor reputation or limited features.

A blacklist check must know which address it is checking. This tool checks the A record, the web host. If your website is hosted on a shared server with a hundred other domains, the check reflects the behaviour of all hundred. If one of those domains runs a phishing campaign, the shared address can be listed, and your domain will show as Listed even though your own content is clean.

The mail server is a different story. Mail servers are usually dedicated IP addresses, or at least addresses shared by a smaller group of customers. Mail reputation follows the sending IP, and recipients' mail servers check that IP against blacklists before accepting mail. A domain can have a perfectly clean web host address and a mail server that is listed on SpamCop because someone on that server sent spam.

This tool cannot help you with the mail server question. It never resolves the MX record, and it never queries the mail server's sending IP. If you need to know why your email is bouncing, you need to find the actual IP address your mail server uses for outgoing connections and check that address against the same twelve zones.

Delisting Steps

When the tool shows a red Listed result, the next question is always how to get the address removed. The tool itself provides no delisting links, so the steps below are general knowledge about how the major blacklist operators handle removal requests. Start by identifying which zone flagged the address, because each operator has its own process.

Confirm the listing still exists. Blacklists expire entries automatically, and many listings disappear within days. Run the check again before you contact anyone. If the address is still listed, visit the operator's website and look for a delisting or removal page.

Understand why the address was listed. The tool shows no reason code, so you may need to query the zone manually or use the operator's own lookup tool. Some operators display the evidence they collected, including sample spam messages or attack logs. That evidence tells you what behaviour triggered the listing.

The third step is to fix the underlying problem. A delisting request for an address that is still sending spam will be rejected. If a compromised server on your network is the source, clean the infection first. If a customer is the source, suspend the account. If the listing came from a shared address, you may not be able to fix the cause at all, because the cause belongs to another tenant on the same server.

The fourth step is to submit the delisting request through the operator's official channel. Be prepared to provide proof that you control the address. Some operators require the request to come from the abuse contact listed in the WHOIS record for the address. Others accept requests from anyone who can demonstrate control through DNS or hosting account access.

UCEPROTECT deserves special mention because its level 2 and level 3 listings are controversial. Those levels list entire provider allocations and whole autonomous systems, which means thousands of innocent addresses can be listed because one customer misbehaved and the provider did not respond fast enough. Delisting at those levels often requires the provider to take action, and UCEPROTECT charges a fee for expedited removal. An individual website owner has little recourse against a level 3 listing beyond contacting the hosting provider and asking them to resolve the underlying abuse report.

Related Tools

When you need to see the actual address behind a domain before running a blacklist check, use the Domain into IP Converter to resolve the A record yourself.

When you want a broader look at whether a domain is associated with malicious activity beyond IP blacklists, the Suspicious Domain Checker examines the domain from a different angle.

When the worry is malware on a website, the Google Malware Checker consults Google's Safe Browsing data to see whether the domain has been flagged for harmful content.

Frequently Asked Questions

What is the difference between a web host IP and a mail server IP?

The web host IP is the address in the domain's A record, which points to the server that delivers the website. The mail server IP is the address in the MX record, which points to the server that handles email. This tool checks only the web host IP, so a clean result says nothing about whether your outgoing email is blacklisted.

Why does my domain show as Listed when I never sent spam?

Your domain's A record may point to a shared hosting address or a Cloudflare edge address used by thousands of other sites. If any of those sites triggered a blacklist operator, the shared address gets listed, and your domain appears Listed even though your own content is clean. Check the Domain IP in the results to see which address was actually evaluated.

Does this tool check Spamhaus?

No. Spamhaus refuses queries that arrive through public resolvers operated by Cloudflare and Google, and it answers those queries with an error code that the tool now correctly treats as Not Listed. Spamhaus was removed from the zone list during the cleanup, so a clean result here does not cover the most widely consulted blacklist operator in the world.

What do the different UCEPROTECT levels mean?

UCEPROTECT level 1 lists a single IP address observed sending spam. Level 2 escalates to the provider's entire allocation when the provider ignores abuse reports. Level 3 escalates to the whole autonomous system number. A level 2 or level 3 listing usually means the hosting provider failed to respond to abuse complaints, not that your specific website is the problem.

How long does a blacklist check take?

A full check takes about five seconds, with live tests measuring a range of roughly five to six seconds. The twelve zones are queried one after another, so a slow zone can stretch the run. Results reflect the moment of the query, and blacklists change constantly, so you should re-run the check if you need current information.

How do I remove my IP from a blacklist?

Identify which zone flagged the address, then visit that operator's website and look for a delisting page. Fix the underlying problem first, because operators reject requests for addresses that are still generating abuse reports. Some operators require the request to come from the abuse contact in the WHOIS record, and UCEPROTECT charges a fee for level 2 and level 3 removals.