Blacklist Checker
A DNSBL check tells you whether an IP address or domain is currently listed on a spam blocklist that mail servers consult before accepting a message. Checking regularly catches a listing early, before it starts silently affecting email deliverability.
Examples: google.com, wikipedia.org, example.com, 1.2.3.4
How to read the result
Each row is one blocklist. 'Listed' means that blocklist currently flags the address; 'Not listed' means it is clean there. Clear across the board is what you want.
Some blocklists barely register with mail providers; others, like Spamhaus, are consulted almost everywhere. A single listing on a major one can be enough to bounce your mail.
Reputation moves. A clean check today does not lock in tomorrow, and a listing can appear the moment a blocklist reacts to a spam run. Re-check if deliverability drops.
How blacklists work
A blocklist (DNSBL) is a published list of IPs and domains a service has judged to be sending spam or abuse. Mail servers query it over DNS in milliseconds before accepting a message.
They let a receiving server turn away known-bad senders before it spends anything on the message. For most of the internet's email this is the first line of spam defence.
Independent operators, each with its own listing rules and reach: Spamhaus, Barracuda, SpamCop, SORBS, and others. This tool checks around thirty of them at once.
Why an address gets listed
Actual spam is the obvious cause, but on shared hosting a noisy neighbour on the same IP can get the whole address listed with you.
A cracked mailbox or a hacked site quietly sending spam is one of the most common causes, and it keeps relisting you until you close the hole.
Missing or broken SPF, DKIM, and DMARC make your mail look forged, which some blocklists treat as a reason to list.
A brand-new sending IP has no reputation to lean on, and a reused one can inherit the reputation of whoever had it before you.
How to get delisted
Delisting before you have stopped the spam just gets you relisted, often faster. Find the compromised account, close the open relay, or repair the auth records first.
Most blocklists have a self-service removal form once the problem is gone, and a few delist automatically after a quiet spell. Spamhaus and Barracuda both take direct requests.
Removal can take minutes or days to reach the servers that cache it. Rebuild reputation by sending clean, wanted mail at a steady rate, not a sudden burst.
The blocklists we check
- Spamhaus
- The most widely trusted blocklist. A listing here reaches almost every major mail provider.
- Barracuda
- Barracuda's reputation list, consulted across their large base of mail appliances.
- SpamCop
- Cisco-run and driven by user spam reports; listings expire fairly quickly once the reports stop.
- SORBS
- A long-running family of lists covering spam sources, open relays, and hijacked ranges.
- Abusix
- A commercial reputation service used by many providers and security tools.
- SpamRATS
- Targets IPs behaving like infected or misconfigured mail hosts.
- SURBL
- A domain-based list that flags links seen in spam, not just sending IPs.
- SenderScore
- A 0 to 100 reputation score for a sending IP, used to decide how much of its mail to accept.
Frequently Asked Questions
What is a DNSBL?
A DNSBL, or DNS-based blackhole list, is a database of IP addresses and domains reported for sending spam or other abusive traffic. Mail servers query these lists in real time and can reject or flag messages from anything listed.
What should I do if I'm listed on a blacklist?
First fix the underlying cause, such as an open relay, a compromised account, or a misconfigured mail server sending unsolicited messages.
Once that's resolved, submit a delisting request to the specific blacklist operator; most publish their own removal process, and being listed on one does not automatically delist you from others.
Does being on one blacklist really matter?
It depends on which list and who uses it.
A listing on a blocklist that major mail providers subscribe to can cause real deliverability problems, while a listing on a smaller or less-used list may have little practical effect.
Checking several lists at once shows which ones actually apply to your situation.
Why is my IP blacklisted?
Usually because mail from it, or from a neighbour sharing it, looked like spam, or a compromised account sent some. New and recycled IPs also get listed simply for having no track record.
How do I get removed from a blacklist?
Fix what caused the listing, then use the blocklist's removal form. Some clear on their own after a quiet spell. Delist without fixing the cause and you will be back on quickly.
How long does delisting take?
Anywhere from minutes to a few days. The blocklist removes you fairly fast; the delay is other servers catching up as their cached copies expire.
Does one blacklist really matter?
It depends which. A minor list few servers consult will not hurt much. A listing on Spamhaus can bounce a large share of your mail on its own.
Will being listed stop my email?
It can. A receiving server that consults the list you are on may reject or spam-folder your messages. Whether it bites depends on which lists flag you and which ones your recipients trust.