What is an IP reputation check?

A look at how receivers judge an IP address. Public blocklists are the part anyone can query, which is what this tool does. Each mailbox provider also keeps its own private reputation for your IPs, which you can only see through the provider's sender tools, such as Google Postmaster Tools.

Why does Spamhaus say "couldn't check"?

Spamhaus blocks free lookups from public and cloud DNS resolvers, which is where our checks run. Instead of reporting a refused query as clean, we say we couldn't check and link to check.spamhaus.org, where Spamhaus answers directly.

My IP is on the Spamhaus PBL. Am I blacklisted?

Not for spam. The PBL lists address ranges, such as home and dynamic broadband, that shouldn't send mail directly to other servers. If you send through Google Workspace, Microsoft 365 or an email platform, a PBL listing on your office IP doesn't affect your mail. It matters only if that IP runs your mail server.

What IP should I check?

The public IP of the server that hands your mail to the recipient. If you send through Google Workspace, Microsoft 365 or an email platform, that's their IP, and they manage its reputation. Check your own IPs when you run a mail server or have dedicated sending IPs.

Can I check an IPv6 address?

Not here. Most of these lists only cover IPv4, so the tool accepts IPv4 addresses. Spamhaus checks IPv6 addresses at check.spamhaus.org.

Is there a free IP blacklist removal tool?

No tool can remove a listing for you; only the list itself can. Removal is free on most lists: fix the cause, then use the removal or lookup page linked on each result. Be wary of anyone charging to delist an IP.

How do I get my IP removed from a blacklist?

Find and fix the cause first: a compromised account, mail to dead addresses or spam traps from an old list. Then use the list's own removal page, linked on each result. Some listings, such as SpamCop's, expire on their own once the problem stops.

IP blacklist check: Spamhaus ZEN, Barracuda, SpamCop and more

An IP blacklist check asks each blocklist, over DNS, whether it lists your sending IP. Enter the IPv4 address your mail is sent from and this tool queries Spamhaus ZEN, Barracuda, SpamCop, PSBL and Mailspike, explains each return code, and links to each list's removal page. If a list refuses our query, it says "couldn't check", not "clean".

You can paste a whole Received header line; the first IP in it is used. For a domain, use the domain blacklist check.

SimpleAPI

Sample result

203.0.113.25 is not listed on SpamCop or Barracuda.

IP address: 203.0.113.25
SpamCop: Not listed
Barracuda: Not listed

What this means for you

A listed IP gets mail refused by many inboxes; a clean result rules that cause out.

Next step:Check the IP's reverse DNS

Spamhaus, Barracuda, SpamCop, PSBL, Mailspike
Every listing code explained
Refused or silent lists shown as unavailable
The exact query, so you can repeat it

IPv4
DNSBL
Blocklist

By SimpleVerifier Team · Last updated October 17, 2026

How do I check if my IP is blacklisted?

Find the IP your mail is sent from. In a message you sent, open the headers and take the IP from the first Received line added by the recipient's server, or paste the line itself.
Enter it and press Check blocklists. Each list gets two DNS queries: one for your IP and one for its official test entry.
Read each row. Listed rows explain what the return code means; Couldn't check rows link to the list's own lookup page.
If you're listed, fix the cause first, then use the list's removal process. The dig command on each row lets you re-check from your own network.

Example

You enter: The sending IP 203.0.113.25.
You get: Not listed on SpamCop or Barracuda, with each list's exact DNS query shown. A list that refuses our query is shown as couldn't check, not as clean.
Limits: IPv4 only, one IP per check and 10 checks a minute per connection.

How does an IP blacklist check work?

It's a DNS lookup: each blocklist (DNSBL) is a DNS zone, and a listed IP has a record in it. To check 203.0.113.25, you reverse its octets and look up 25.113.0.203.zen.spamhaus.org. "Not found" means not listed; an answer in 127.0.0.x means listed, with the last number saying why. The format is standardised in RFC 5782, which also requires every list to answer for the test address 127.0.0.2 so anyone can confirm the list is working.

Each row shows the exact query, so you can repeat it with dig +short from your own network. Answers in 127.255.255.x are errors, not listings: Spamhaus documents .254 for a query through a public or open resolver and .255 for too many queries in its DNSBL usage FAQ.

Is my IP blacklisted by Spamhaus?

For a definite answer, check it at check.spamhaus.org: Spamhaus refuses free queries from large public and cloud DNS resolvers under its fair use policy, and our checks run on cloud servers. Some resolvers return the refusal as an error code; others turn it into "not found", which looks exactly like a clean result. Many checkers report that as clean. We don't: alongside your IP we query each list's 127.0.0.2 test entry, and if that doesn't come back listed, the list isn't answering us honestly, so your result for it is "couldn't check".

Domains are listed separately, on lists such as the Spamhaus DBL; check those with the domain blacklist check. This page covers sending IPs, which receiving servers look up the moment your server connects.

What does it mean if my IP is blacklisted?

It means a list has seen mail from that IP that looked like spam, or, on the Spamhaus PBL, only that the range shouldn't send mail directly. On Spamhaus ZEN, 127.0.0.2 is the SBL (listed by Spamhaus staff), .3 is CSS (automated, low-reputation sending), .4 to .7 are the XBL (an infected or hijacked machine), .9 is DROP, and .10 or .11 is the PBL. The PBL isn't an accusation: it lists ranges, such as home broadband, that shouldn't run a mail server, so a PBL hit on an office IP that sends through Google Workspace or Microsoft 365 is expected. Our guide to Spamhaus listings covers each one.

Barracuda, PSBL and Mailspike list IPs that sent to their traps or scored badly; SpamCop lists IPs reported by its users, and its listings expire on their own once reports stop. Whatever the list, the cause is usually the same: mail to addresses that don't exist, spam traps on an old or bought list, or a compromised account sending spam. Fix that first, then follow how to get off a blacklist. Requests made while the problem continues tend to fail.

Is an IP blacklist different from a domain blacklist?

	IP blocklist	Domain blocklist
What is listed	The sending server's IP address	Domains in the From address, links or headers
When receivers check it	When your server connects	When the message content is read
Examples	Spamhaus ZEN, Barracuda, SpamCop	Spamhaus DBL, SURBL, URIBL
Who can fix it	Whoever controls the IP; your platform if it's shared	You, as the domain owner
Check it with	This tool	The domain blacklist check

Who uses this tool, and for what?

IT admins: When users report bounces mentioning Spamhaus or a block list, check the mail server's IP, read which list and which code, and follow that list's removal process.
Cold emailers: Check any dedicated IP or VPS before warm-up and again whenever replies drop, alongside its reverse DNS.
Agencies: Run a client's sending IPs during an audit, and explain a PBL hit on an office IP before anyone panics about it.
SaaS teams: Check the IPs your app sends receipts and password resets from. A listing there shows up as support tickets about missing emails.

What can’t this tool tell you?

Five public lists only. Gmail, Outlook and Yahoo keep their own private reputation data, which no outside lookup can see.
IPv4 only. IPv6 addresses are rejected, with a pointer to Spamhaus's own lookup.
Spamhaus often shows "couldn't check" from our servers. That is a refused query, not a result.
Not listed is not the same as a good reputation. A new or unlisted IP can still have its mail filtered.
It checks IPs. Domains in your links and From address are on separate lists; use the domain blacklist check.

Common questions

How do I check if my IP is blacklisted?: Enter the IPv4 address your mail is sent from above. The tool queries Spamhaus ZEN, Barracuda, SpamCop, PSBL and Mailspike over DNS and shows listed, not listed or couldn't check for each, with what any listing code means.
What is an IP reputation check?: A look at how receivers judge an IP address. Public blocklists are the part anyone can query, which is what this tool does. Each mailbox provider also keeps its own private reputation for your IPs, which you can only see through the provider's sender tools, such as Google Postmaster Tools.
Why does Spamhaus say "couldn't check"?: Spamhaus blocks free lookups from public and cloud DNS resolvers, which is where our checks run. Instead of reporting a refused query as clean, we say we couldn't check and link to check.spamhaus.org, where Spamhaus answers directly.
My IP is on the Spamhaus PBL. Am I blacklisted?: Not for spam. The PBL lists address ranges, such as home and dynamic broadband, that shouldn't send mail directly to other servers. If you send through Google Workspace, Microsoft 365 or an email platform, a PBL listing on your office IP doesn't affect your mail. It matters only if that IP runs your mail server.
What IP should I check?: The public IP of the server that hands your mail to the recipient. If you send through Google Workspace, Microsoft 365 or an email platform, that's their IP, and they manage its reputation. Check your own IPs when you run a mail server or have dedicated sending IPs.
Can I check an IPv6 address?: Not here. Most of these lists only cover IPv4, so the tool accepts IPv4 addresses. Spamhaus checks IPv6 addresses at check.spamhaus.org.
Is there a free IP blacklist removal tool?: No tool can remove a listing for you; only the list itself can. Removal is free on most lists: fix the cause, then use the removal or lookup page linked on each result. Be wary of anyone charging to delist an IP.
How do I get my IP removed from a blacklist?: Find and fix the cause first: a compromised account, mail to dead addresses or spam traps from an old list. Then use the list's own removal page, linked on each result. Some listings, such as SpamCop's, expire on their own once the problem stops.

Sources

Authentication and capacity are half of deliverability.

The other half is who you send to. Every hard bounce counts against the domain and inboxes you are sending from, and nothing in DNS can tell you which addresses on your list are dead.

Bulk verification with real SMTP mailbox checks
Hard bounces removed before a send, not discovered after
Catch-all, disposable and role detection on every row

Get started — $29.99/mo See the published limits first

One plan, cancel anytime, no contract. Sign in with Google and your first 100 email checks are free, no card. The free tools stay free either way.