Blacklist checker

Check an IP address or a domain's mail servers against active DNS blocklists. Every list is self-tested before use, so lists that have shut down never raise false alarms, and each listing comes with its reason.

  • 24 IP lists and 2 domain lists
  • Dead or broken lists left out
  • Reverse DNS checked too
See every list
Ready

Blocklist status

Enter an IP or domain

IP —
PTR —
Listed
—
Not listed
—
Not available
—
  1. Target
    Waiting for input
    IP or domain
  2. Self-test
    —
    Lists that work today
  3. Lookup
    —
    Parallel DNS queries
  4. Result
    —
    Listings with reasons

Blocklist report

Built and maintained by Bhavin J. Sheth

Last updated . Live DNS queries to each list.

Enter an IPv4 address or a domain above to see which active blocklists list it, why, and how to get removed, plus its reverse DNS.

Fair-use limit: 20 checks per hour and 100 per day for each visitor IP address. Results are cached for 10 minutes. A domain check covers up to 4 IPs.

How DNS blocklists work

Mail servers ask blocklists about every connecting IP through ordinary DNS lookups, in a fraction of a second.

A question in DNS form

To check 203.0.113.10, a server looks up 10.113.0.203 under the list's zone. An answer in 127.0.0.x means listed; no answer means not listed.

IP, range and domain lists

Most lists cover single IPs. Some cover whole ranges or networks, and domain lists check names found in links inside messages.

Listed is not blocked everywhere

Each mail provider picks its own lists. A listing on a small list may affect few servers; a big list can affect many.

Lists come and go

Dead lists can answer for every IP. RFC 5782 requires test entries, which this tool checks before trusting any list.

The lists this tool checks

Each one is tested with its standard test entries before it is used.

ListCoversWhat it lists
SpamCop
bl.spamcop.net		 Single IP IPs reported by SpamCop users; listings expire on their own once reports stop.
Barracuda BRBL
b.barracudacentral.org		 Single IP IPs that sent spam to Barracuda's network of mail filters.
UCEPROTECT Level 1
dnsbl-1.uceprotect.net		 Single IP Single IPs that sent mail to UCEPROTECT spam traps.
UCEPROTECT Level 2
dnsbl-2.uceprotect.net		 IP range Whole IP ranges with many Level 1 listings, so neighbours can be listed too.
UCEPROTECT Level 3
dnsbl-3.uceprotect.net		 Whole network Whole networks (ASNs) with many listings. Few mail servers use it.
PSBL
psbl.surriel.com		 Single IP IPs that sent mail to spam traps; anyone can remove a listing on the site.
Mailspike
bl.mailspike.net		 Single IP IPs with a poor sending reputation.
DroneBL
dnsbl.dronebl.org		 Single IP Infected hosts, open proxies and other abused machines.
SpamRATS
all.spamrats.com		 Single IP IPs with no reverse DNS, dynamic-looking names or seen sending spam.
Blocklist.de
bl.blocklist.de		 Single IP IPs reported for attacks on mail, SSH, web and other servers.
JustSpam
dnsbl.justspam.org		 Single IP IPs seen sending spam.
Backscatterer
ips.backscatterer.org		 Single IP Servers that send bounces or auto-replies to forged senders.
NordSpam
bl.nordspam.com		 Single IP IPs seen sending spam.
SpamEatingMonkey
bl.spameatingmonkey.net		 Single IP IPs seen sending spam.
SpamEatingMonkey Backscatter
backscatter.spameatingmonkey.net		 Single IP Servers that send backscatter.
GBUdb Truncate
truncate.gbudb.net		 Single IP IPs that send almost nothing but spam to GBUdb's filters.
InterServer RBL
rbl.interserver.net		 Single IP IPs that attacked or spammed InterServer's network.
Suomispam
bl.suomispam.net		 Single IP IPs seen sending spam.
VirusFree.cz
bip.virusfree.cz		 Single IP IPs seen sending viruses or spam.
SPFBL
dnsbl.spfbl.net		 Single IP IPs with a bad sending reputation.
0spam
bl.0spam.org		 Single IP IPs seen sending spam.
s5h.net
all.s5h.net		 Single IP IPs seen sending spam.
Woody's SMTP blacklist
blacklist.woody.ch		 Single IP IPs seen sending spam.
RBL.JP virus
virus.rbl.jp		 Single IP IPs seen sending viruses.
SURBL
multi.surbl.org		 Domain Domains found in spam, phishing and malware messages.
URIBL
multi.uribl.com		 Domain Domains found in the body of spam messages.

How to use this tool

From an IP or domain to a list of what to fix.

  1. Enter an IP or domain

    For a domain, the tool finds its website IP and the IPs of its mail (MX) servers.

  2. Lists are tested first

    Each blocklist must answer its standard test entries correctly, or it is left out.

  3. All lists are asked at once

    Parallel DNS queries go to every working list, so a check takes a few seconds.

  4. Read the reasons

    Listings show the return code, its meaning, the list's reason text and its removal page.

What this tool does, and what it doesn't

A plain list, so you know exactly what to expect.

This tool does

  • Check active IP and domain blocklists
  • Self-test every list before use
  • Check website and MX server IPs
  • Show return codes and reasons
  • Link to each list's removal page
  • Check reverse DNS both ways

This tool does not

  • Request delisting for you
  • Check private lists of Gmail or Outlook
  • Check Spamhaus or IPv6 addresses
  • Test SPF, DKIM or DMARC
  • Guarantee inbox placement
  • Monitor IPs over time

Where your data goes

Our server sends DNS queries for the IP or domain to each blocklist through its own resolver, so the list operators see those lookups. Results are cached for 10 minutes, and nothing else is stored. Fair-use counters use a hashed IP address, as described in our privacy policy.

How DNS blocklists work (RFC 5782)

Why your results might look unexpected

The six situations people run into most, and what each one means.

Listed only on UCEPROTECT Level 2 or 3

These cover whole ranges or networks. Other customers caused it; ask your provider.

SpamRATS says no reverse DNS

Ask the owner of the IP, usually your host, to set a PTR record that names your mail server.

Some lists are not available

They failed their daily self-test, refuse our resolver or did not answer in time.

The domain check shows a web server

Websites and mail often use different IPs. Check the sending IP from a message header.

Listed on many lists at once

A strong sign of a compromised account, website or computer sending mail.

A bounce names a list not shown here

Providers such as Microsoft and Spamhaus have their own lookups. Check there directly.

Questions about blacklists

What is a DNS blocklist?

A DNS blocklist, also called a DNSBL or RBL, is a list of IP addresses or domains linked to spam or abuse, published through DNS. A receiving mail server asks the list about the connecting IP; if the list answers, the server may reject the message or score it as spam. Each mail provider chooses which lists to trust, so a listing affects only the servers that use that list.

Which lists are checked, and why not more?

The tool checks active public lists and tests each one daily with its standard test addresses. Lists that shut down can start answering for every IP, which other checkers then report as a listing: SORBS closed in June 2024 and NiXSpam in January 2025. Such lists are shown as not available instead. Spamhaus is not checked here, because its free public lists are only for non-commercial use and refuse queries from shared hosting. Use the free lookup on check.spamhaus.org instead.

My IP is listed. What should I do?

First find and fix the cause: a hacked website or mailbox, an open relay, malware on a computer behind the IP, or a script sending unwanted mail. Then follow the removal link in the result; many lists expire listings on their own once the problem stops. For range or network listings such as UCEPROTECT Level 2 and 3, ask your hosting provider, because the cause may be other customers.

Why is my IP listed if I never sent spam?

On shared hosting and cloud servers, the IP may have been used by someone else before you, or be shared with other senders now. Some lists also cover whole ranges or networks, or list IPs that look residential or have no reverse DNS. Check the code meaning and the list's reason text to see which case applies.

I am not listed, but my emails still go to spam. Why?

Blocklists are only one signal. Gmail, Yahoo and Outlook also look at SPF, DKIM and DMARC authentication, your domain's reputation, complaint rates and how recipients engage with your mail. Since 2024, Gmail and Yahoo require authentication for bulk senders. Check your DNS records and, for Gmail, Google Postmaster Tools.

Which IP should I check for an email problem?

The IP your mail is sent from, which is often not your website's IP. You can find it in the Received lines of a message's headers, or in a bounce message. When you enter a domain, the tool checks its website IP and the IPs of its MX servers, which receive mail and often also send it.

Is my query stored or shared?

Our server sends DNS queries for the IP or domain to each blocklist, so the list operators see those queries coming from our server, as with any blocklist lookup. Results are cached for 10 minutes so repeated checks do not query the lists again, and fair-use counters use a hashed version of your IP address, as described in our privacy policy.

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