Email Blacklist Check: Domain, Address and IP
Seventeen blocklists in one query: Spamhaus, Barracuda, SpamCop and the rest. Every list is shown with the answer it gave, including the ones that declined our query or stayed quiet.
Takes a domain, an IP address or an email; the type is detected for you. No signup.
Zones we query
- zen.spamhaus.org
- b.barracudacentral.org
- bl.spamcop.net
- truncate.gbudb.net
- dnsbl-1.uceprotect.net
- bl.mailspike.net
- bl.spameatingmonkey.net
- backscatter.spameatingmonkey.net
- rbl.interserver.net
- all.s5h.net
- rbl.blockedservers.com
- bl.0spam.org
- spam.dnsbl.anonmails.de
- bl.suomispam.net
- ips.backscatterer.org
- dbl.spamhaus.org
- multi.surbl.org
Each zone was verified with a test vector: a list that has ceased to exist answers with the same “no such name” as a list you are not on. Try , , .
What an email blacklist is
A blacklist, also called a blocklist or a DNSBL, is a database of addresses and domains caught sending spam. The receiving server consults it before accepting a message. Gmail, Outlook and Yahoo make that query on every delivery, and it takes milliseconds.
There are two kinds. Address lists block the machine your mail leaves from. Domain lists look at the name inside the message, so a domain from your links can get a message rejected while the sending server is spotless.
Why addresses end up listed
Listings are rarely accidental. Each one has a cause, and while the cause is alive a removal request only wastes your time.
Recipients hit the Spam button. Above 0.1% of a campaign is already dangerous territory.
A hard bounce rate over 5% tells the lists the sender is not maintaining a list at all.
Decoy addresses. Mail arriving at one proves the list was not collected by you.
On an ESP's shared address one client spams and everyone on that IP pays for it.
A hundred messages yesterday, fifty thousand today. From outside that looks like a breach or a bought list.
Automation retrying failed deliveries runs the counters up overnight.
The lists that actually block mail
They are not equal. A handful decide whether large receivers accept your connection at all, the rest feed scoring systems where a hit costs a fraction of a point.
- Spamhaus ZENThe one that matters most. It combines SBL, XBL, CSS and PBL, and a listing gets mail rejected outright at a large share of the internet.critical
- BarracudaSits in front of a great many corporate mail systems, so it shows up on B2B campaigns.high
- SpamCopFed by user reports; entries expire on their own a day or two after the sending stops.high
- Spamhaus DBL and SURBLDomain lists. They catch the name in your links even when the sending server is clean.high
The Spamhaus zones and how they differ
Five lists run under one name, and removal works differently on each. The report above shows the answer code, and the code tells you which one fired.
- SBLSpam sources. Entries come from real campaigns and are lifted by hand after a review.127.0.0.2
- CSSSending to bought lists and mailing without confirmed consent. The most common case among marketers, and it arrives quietly, without a single recipient complaint.127.0.0.3
- XBLCompromised machines and open proxies. If you are here, look for a breached server or a workstation on your network.127.0.0.4
- PBLRanges that are not supposed to send mail directly: home and dynamic addresses. You land here for the kind of address you have, not for anything you did.127.0.0.10-11
- DBLA list of domains rather than addresses. A domain lands there for what your messages say and for the links inside them.127.0.1.x
ZEN is not a sixth list, it queries the first four at once. That is the name bounce messages usually carry, so read the code rather than the name: it says which of the four fired and what needs fixing.
PBL is not what people think it is
Of all the listings, this one causes the most confusion and the most wasted effort. A PBL entry does not say you sent spam. It says the address belongs to a range that should not be sending mail directly: a home connection, a dynamic pool, consumer broadband.
There is usually nothing to appeal, because the listing is accurate. If you are sending from a dynamic address, that is the problem, and removal would not fix it: receivers distrust the range, not the entry. The answer is to send through a mail server with a static address and proper reverse DNS, or through your provider's relay.
This is also why a PBL hit shows up so often on tests run from an office or a laptop. The connection is doing exactly what PBL describes.
Listed on a blocklist: how to get removed
- Find where you are listed
The check above queries seventeen lists and shows what each one answered, including the ones that stayed quiet. A single small list rarely matters; Spamhaus is felt immediately and everywhere.
- Work out the cause
A compromised mailbox, a web form with no rate limit, a bought list, a script retrying in a loop. A request filed while the cause is alive is pointless, because the listing returns within days.
- Fix it
Change passwords, close the open relay, clean the list, check SPF, DKIM and DMARC.
- Request removal
Every hit in the report links to the right page. Spamhaus clears most automated listings in hours, SpamCop expires on its own, Barracuda reviews requests by hand.
How to stay off the lists
Repeated removals from the same address are themselves a signal, so not coming back is the cheaper option.
- Verify the list before every send traps and dead addresses get filtered out before the send, not after the bounces
- Use double opt-in confirmation costs you a quarter of signups and leaves real people in the list
- Warm up new addresses two hundred messages, four hundred, eight hundred, starting with your most engaged
- Watch the numbers bounces above 2% are a warning, complaints above 0.1% are a reason to act today
- Drop inactive subscribers prune by engagement rather than bounces alone: a recycled trap looks like an ordinary address
- Never buy a list a bought list contains traps for certain, and the months of reputation repair are yours
Why we show every list, not just the hits
“You are not blocklisted” is a claim nobody can check. It does not say how many lists were consulted, whether they answered, or whether the important ones were among them. Two lists queried and twenty read the same way in a summary and mean entirely different things.
So every list appears with its own answer: listed, clean, declined our query, did not respond. That last distinction matters more than it looks. Treating a refusal as a pass hands out clean bills of health on no evidence, treating it as a hit accuses everyone.
The roster of seventeen zones was not found on the web, it was tested. Each zone was queried with its own documented test point and with a control value that must come back clean. That check is not ceremony: a dead zone returns the same “no such name” that means “not listed”, so a list that quietly disappeared will clear every address forever. SORBS closed in 2024 and still appears in roster after roster of tools that never went back to look.
How this differs from MXToolbox and multirbl
The tools overlap, and saying plainly how we differ is easier than pretending we do not. MXToolbox checks a longer roster and does a great deal besides, from DNS and MX to SMTP diagnostics and monitoring, while multirbl goes wider still, close to two hundred sources, and includes lists nobody has used in years.
We deliberately query seventeen and show what each one answered, including those that stayed quiet. An answer of “not found” means nothing without knowing who was asked.
Blocklist questions
How long does removal take?
It depends. SpamCop clears entries on its own a day or two after the sending stops, Spamhaus removes most automated listings within hours though a manual review there can take up to a week, and Barracuda usually answers within a day of approving a request. UCEPROTECT level 3 has no manual removal at all, the entry expires on its own schedule. A listing that returns after removal means the cause is still there.
What is the difference between the PBL and the SBL?
The SBL lists addresses seen sending spam. The PBL lists addresses that should not be sending mail directly at all: home connections, dynamic ranges, anything a provider has marked as end-user space. A PBL entry is not an accusation and there is usually nothing to appeal. The fix is to send through a mail server or your provider's relay rather than straight from that address.
My IP is clean but mail still goes to spam. Why?
Blocklists are a small part of the decision. Providers weigh authentication, domain reputation, complaint rates, how recipients engage with your mail, and the content itself. A clean IP means no receiver will reject you outright at connection time. Everything after that is decided per message.
Should I check the domain or the IP?
Both, and they answer different questions. IP lists say whether the machine sending your mail is trusted. Domain lists say whether the name in your links and your From address is trusted. Enter a domain here and we resolve its MX hosts and check those addresses, because that is where the mail actually leaves from.
The listed IP belongs to my provider, not to me. What now?
On shared hosting that is common, and you cannot request removal for an address you do not control. Your options are to ask the provider to deal with it, to move to a dedicated address, or to send through a service with its own reputation. Sharing an address with a spammer is a real deliverability problem however well your own domain is configured.
Do I need to check all hundred-plus lists?
No. A long roster creates a false sense of coverage: half the sources in it either have no effect on deliverability or serve stale data. If the question is whether your mail will land, the lists mail providers actually rely on are enough. If the question is an audit checklist, use a tool with the long roster.
Why do some lists show as declining our queries?
Most blocklists limit free use and refuse queries from resolvers they have not authorised, answering with a reserved code rather than a verdict. That is a fact about where this service is hosted, not about your address. We report those separately rather than counting them as a pass or a failure, because a list that did not answer has told you nothing either way.
Read next
A clean address does not help when the list is full of mailboxes that no longer exist, because bounces are what get you listed again. uChecker verifies your list before you send, the first 100 addresses free.