An IP blacklist checker scans your IP address against dozens of DNS-based blacklists (DNSBLs) — the lists mail servers and security tools use to flag spam or malicious sources.
If your IP is on even one, your emails may bounce, get flagged as spam, or never arrive at all. Konetix checks your IP against 100+ DNSBLs in real time, free.
Konetix checks major blacklists like Spamhaus, Barracuda, SpamCop, and UCEPROTECT, along with mailbox provider lists from Microsoft, Yahoo, and AOL.
In total, the scan covers more than 100 lists, so you get a full picture instead of checking each one by hand.
1. Sign up free - no credit card required.
2. Enter the IP address or subnet you want to check.
3. Get results in seconds - see exactly which blacklists (if any) have flagged you, with direct links to delist.
IPs get blacklisted for a few common reasons. It is not always something you did wrong.
Spam complaints are the most direct cause. If enough people mark your mail as spam, blacklists take notice.
A hacked server is another big cause. If someone breaks into a mail server or website on your IP and starts sending spam through it, the IP gets flagged, even though you were not the one sending it.
If you use shared hosting or a shared IP pool, a "bad neighbor" can get your whole range listed.
That is one reason range wide monitoring matters more than checking a single IP. A misconfigured mail server can also cause problems.
Things like an open relay, missing reverse DNS, or no SPF, DKIM, or DMARC records can get you flagged before you ever send a single spam email, just because the setup looks risky.
The impact depends on which list flagged you. At minimum, some of your mail will land in spam folders instead of the inbox.
On more serious lists like Spamhaus, whole mail servers may reject your messages outright.
There is no bounce message, no spam folder. The email just never arrives.
For a business, this often shows up as missing password resets, receipts, or notifications, along with confused customers and support tickets asking "did you get my email?" before anyone realizes a blacklist is the real cause.
The free scan checks one IP or a small subnet on demand. It is good for a quick, one time check.
Paid monitoring runs every night across your whole IP range. You find out the moment any address gets listed, instead of waiting for a customer to complain.
If you manage more than a few IPs, like an ISP, host, or MSP, ongoing range monitoring is the real upgrade. A single bad IP in a large block is easy to miss with manual checks.
Run it through the free checker above. Results are instant and show every blacklist that lists it, if any.
It depends on the list. Some blacklists clear listings on their own within 24 to 48 hours if no new complaints come in. Others, like Spamhaus, require a manual request and can take longer.
Yes, though how much depends on the list. A listing on a major list can get your mail rejected outright. A listing on a small, obscure list may barely matter.
Yes. Enter a subnet instead of a single IP to scan the whole range at once.