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BlocklistChecker
Check any domain and its mail server IPs against major DNS blocklists like Spamhaus, SpamCop, and Barracuda. Free, no account needed. The domain and the IP are checked separately, because a listing on each has a different cause.
14-day free trial · no credit card · cancel anytime
DNS blocklists (DNSBLs) are the lists mail servers query before accepting a message: Spamhaus, SpamCop, Barracuda and dozens more. A listing can mean outright rejection at major receivers, silently, from one day to the next.
Your domain and your sending IPs are checked separately, because they get listed for different reasons: domains for spam content and spoofing patterns, IPs for the behavior of whoever sent from them, including previous tenants.
How it works
- 01Enter the domain. The checker resolves its MX records to the mail server IPs behind them.
- 02The domain and each IP are queried against the common DNSBL zones, the same way a receiving mail server queries them during delivery.
- 03Listings are reported per zone with the zone meaning, since a Spamhaus PBL listing (policy, often fixable in minutes) is a very different problem from a SBL listing (evidence of spam traffic).
- 04Authenticated accounts scan an expanded set of zones, matching what the larger receivers consult.
When to use it
Mail to specific providers stopped arriving or started bouncing, which is the classic symptom of a fresh listing.
After any sending burst, a security incident, or on a domain you recently acquired, to catch inherited IP reputation.
Common mistakes
Checking only the domain
Most listings are on IPs, not domains. If you check only example.com you will miss the listing on the mail server that actually sends your mail. Always resolve MX and check the IPs behind them.
Delisting without fixing the cause
Most zones re-list quickly when the underlying behavior continues. A listing is a symptom: warmup done too fast, a compromised account, a burst to a stale list. Fix the cause first, then request removal.
Ignoring the small lists
You cannot subscribe only to the lists that matter. Small and regional zones feed aggregators and middlewares that large receivers consult, so an obscure listing can still cost delivery somewhere that matters to you.
Treating a one-time check as monitoring
Listings appear between checks, and the damage starts with the first rejected message. A one-off scan tells you today state; continuous monitoring with alerts is what keeps a listing from costing you a week of deliverability.
Frequently asked questions
What is a DNSBL (DNS blocklist)?
A DNS zone that mail servers query during delivery: if the sending IP or domain has an entry, the server rejects or scores the message. Zones differ in what gets you listed and who trusts them, from evidence-based lists like Spamhaus SBL to policy lists like PBL.
Which blocklists does the checker query?
The common zones receivers consult, including Spamhaus, SpamCop and Barracuda, queried exactly the way a receiving mail server queries them. Signed-in accounts scan an expanded zone set.
How does a domain or IP end up listed?
Spam traps hit from a stale list, complaint spikes, sending bursts that look like spam, a compromised mailbox sending on its own, or simply inheriting an IP with history. Policy lists like PBL also list IPs that should not be sending direct mail at all.
How do I request removal from a blocklist?
Each zone has its own removal process; many are self-service and free (Spamhaus, SpamCop), some require the operator. The sequence is always: find the listing reason, fix the cause, then request removal. Re-listing with the cause unfixed is fast.
Why check the MX IPs and not just my domain?
Receivers list and check IPs far more than domains, and your sending IP is shared infrastructure unless you pay for dedicated. The IP can carry a listing from before you ever used it, which is why the checker resolves MX and scans each IP.
My mail still lands in spam but nothing is listed. What now?
Blocklists are one filter among several. With no listings, move to authentication (SPF, DKIM, DMARC alignment), content scoring, and the receivers own reputation signals like Google Postmaster data. A full health check covers the public-side basics in one pass.
From the blog
- Why Do My Emails Go to Spam in Outlook but Not Gmail?Gmail and Microsoft judge your mail separately. Outlook cares more about your sending IP, and complaints there stay invisible until you turn on JMRP.
- My Customers Say They Never Got My Email. Where Did It Go?'Delivered' in your platform's log means the receiver accepted the message, not that it arrived. Four states, and one question that settles most of them.
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