Free Email Blacklist Check

IP blacklist check: is your server on a DNSBL?

An IP blacklist check queries the DNS-based blocklists (DNSBLs) that mailbox providers consult when your email arrives. If your sending IP appears on a list the receiver trusts — Spamhaus ZEN above all — your messages can be rejected outright or silently routed to spam, no matter how good the content is.

The mechanics are simple: your IP's octets are reversed and looked up as a hostname under each blacklist's zone (so 203.0.113.10 becomes 10.113.0.203.zen.spamhaus.org). A 127.0.0.x answer means listed; no record means clean. This tool runs that exact query against 8 major blacklists in parallel, live from your browser.

Not every listing is equal. Spamhaus is used by most of the world's mail servers, while smaller lists like UCEPROTECT affect far fewer receivers. The results table shows you exactly which lists flagged you so you can judge the real impact.

Email domain blacklist checker: check by domain, not just IP

Don't know your sending IP? Enter your domain instead. The tool resolves the domain to its IP address via live DNS and runs the same blacklist check against it — the fastest way to run an email blacklist check when all you have is a company name.

One caveat: if your email is hosted with Google Workspace or Microsoft 365, the IP that actually sends your mail is shared infrastructure managed by the provider, not the IP your website resolves to. In that case the check tells you about your web host, while your deliverability depends mostly on your domain's own reputation and authentication (SPF, DKIM, DMARC).

MX blacklist checker: what your MX records reveal

When you check a domain, the tool also looks up its MX records to identify who actually handles its email. That MX-based context matters: a domain whose MX points at aspmx.l.google.com sends from Google's shared IP pools, and one pointing at protection.outlook.com sends through Microsoft's.

If your MX points at your own mail server, the specific IP of that server is exactly what you should be checking — and monitoring. Self-hosted senders get listed far more often than provider-hosted ones, because one compromised account or one bad send lands directly on your IP's record.

What gets an IP or domain listed on a blacklist

The fastest route onto a list is hitting a spam trap. There are two kinds, and both are a verdict on your list hygiene. Pristine traps are addresses seeded around the web that were never real inboxes — mailing one proves you scraped or bought your list. Recycled traps are real addresses a provider abandoned and then reactivated as traps after a long dormancy — mailing one proves you keep emailing contacts you never clean. Even a handful of hits can put a sending IP on Spamhaus.

The other big triggers are complaints and bounces. Report-driven lists like SpamCop are fed directly by recipients hitting the 'report spam' button and by trap networks, so a climbing complaint rate can land you there within hours. A high hard-bounce rate from an unverified list signals bad hygiene to every receiver, and sudden volume spikes from a cold IP or a compromised mailbox relaying spam do the same. Running your list through an email verifier before you send strips out the dead addresses and hard bounces that recycled traps hide in, which is the single most effective way to stay off these lists.

How to delist from Spamhaus, SpamCop, Barracuda and UCEPROTECT

Every list has its own removal process, and using the wrong one does nothing. Spamhaus ZEN is really several lists rolled together, so start at spamhaus.org/lookup to see exactly which one flagged you. An SBL or CSS listing (a spam source or snowshoe pattern) needs the root cause fixed first, then a removal request through the SBL form. An XBL listing means the IP looks compromised — malware or an open proxy — so clean the machine, then self-remove. A PBL listing isn't a spam accusation at all: it marks a range that shouldn't be sending mail directly, such as residential or dynamic space, so either relay through your provider's smart host or self-remove if it genuinely is a mail server.

The other lists are simpler. SpamCop and UCEPROTECT Level 1 both expire on their own — SpamCop about 24 hours after reports stop, UCEPROTECT roughly 7 days after the last incident — so the fix is to stop the spam and wait, not to buy express delisting. Barracuda processes a manual removal request but requires the IP to have valid reverse DNS (a PTR record) before it will accept one. Self-service lists like PSBL let you pull the IP yourself in seconds once it's clean. In every case, requesting removal before you've fixed the cause just resets the clock until you're relisted.

How a blacklist listing affects your inbox placement

A listing hurts in one of two ways, depending on the receiving server. Servers set to block on a DNSBL hit reject your message outright at connection with a 5xx error, so it never arrives at all — this is common on self-hosted Postfix and Exchange servers and on filtering appliances like Barracuda and Proofpoint. Servers that treat the list as one scoring signal instead accept the message and drop it into the spam folder. Either way, your content never gets a fair read.

How much a listing costs you depends on who your recipients use. A large share of business email runs on self-hosted or gateway-filtered servers that query Spamhaus ZEN directly, which is why a Spamhaus listing is so damaging. Gmail and Outlook.com lean more on their own internal reputation systems than on public DNSBLs at SMTP time, so a listing there is more a symptom than the direct cause — but the same behavior that got you listed is already eroding your standing with them. Once you're delisted, confirm the rest of your setup with an email deliverability test so authentication and reputation aren't quietly working against you too.

IP reputation vs domain reputation: why both matter

This tool checks IP reputation: DNSBLs list the IP address — or, for policy lists, an entire range — that connects to send your mail. Domain reputation is a separate track. Domain-based lists such as Spamhaus DBL and URIBL flag the domains that appear in a spam message's links and body rather than the sending IP, and Gmail and Microsoft each track the standalone reputation of your From domain across every IP you send from.

Which one you need to worry about follows your setup. On shared provider infrastructure like Google Workspace or Microsoft 365, you don't control the sending IP and it's very rarely the problem, so your deliverability rides almost entirely on your domain's reputation and authentication (SPF, DKIM and DMARC). On a dedicated IP you own, both matter: the IP can be blacklisted independently of a spotless domain, and a strong IP won't rescue a domain that's burning its reputation with bad sends. That's why a clean blacklist result is necessary but not sufficient — pair it with proper authentication and disciplined list hygiene.