Free tool

Blacklist checker

Whether the IP sending your email is on Spamhaus, Barracuda or other lists, and how to get off them.

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Reference

How it works and how to read it

A blacklist collects IPs and domains that have sent spam. The server receiving your email checks it for every message and, depending on the answer, accepts it, sends it to spam or rejects it.

The query

The IP, reversed, as if it were a domain

To find out whether 203.0.113.10 is on Spamhaus, the server queries 10.113.0.203.zen.spamhaus.org. If that name doesn't exist, the IP is clean. If it answers with a 127.0.0.x address, it's listed, and the last number says why.

What Spamhaus answers

zen.spamhaus.org

doesn't exist

the IP isn't on the list

127.0.0.2

SBL: known spam source

127.0.0.4

XBL: infected computer or open proxy

127.0.0.10

PBL: range that shouldn't send directly

127.255.255.254

I won't answer you: public DNS

The catch

Spamhaus doesn't answer just anyone

If the query comes through a public DNS, such as Google's, Spamhaus says the name doesn't exist: the same as for a clean IP. That's why we query each list's servers directly, as a mail server does, and also ask for the test IP, which is always listed. If it doesn't show up, that list doesn't count as clean.

Four possible answers

Listed

the list includes it, with its code

Clean

not listed, and the test IP does show up

Denied

the list won't let us query it

No response

didn't answer in time

The weight

Not all lists carry the same weight

Spamhaus and Barracuda are checked by a huge number of servers: being on them usually means rejections. Others, such as UCEPROTECT or DroneBL, are hardly used by anyone to decide. And Gmail and Outlook rely mainly on their own reputation for each IP and each domain, which doesn't appear on any public list.

How much each list matters

Spamhaus ZEN

checked by a huge number of servers

a lot

Barracuda

common in businesses and universities

a lot

SpamCop

expires on its own after 24 hours

somewhat

UCEPROTECT level 1

expires on its own after 7 days

little

FAQ

What is an email blacklist?

It's a database of IPs or domains that have sent spam, which mail servers check via DNS (that's why they're called DNSBLs or RBLs) every time a message arrives. If the sending IP is on the list, the server can reject the message, send it to spam or give it negative points: it depends on the list and who uses it. IP lists look at where the message comes from; domain lists, such as the Spamhaus DBL, look at the sender and the links it contains.

Which IP should I check, the website's or the email's?

What matters is the IP your email is sent from. If you send with your hosting's email, it's usually the server's IP, which is often the same as the website's. If you use Google Workspace, Microsoft 365 or another provider, you send from their IPs and they take care of their reputation. If you type a domain, we check the IP of its website and those of its mail servers (the MX records, which are the incoming ones). To know for sure which IP your email is sent from, send a message to our email test.

Why is my IP on a list if I don't send spam?

Almost always because someone has done it from that IP without you knowing: a website with an unprotected form, a vulnerable plugin someone uses to send email, or an email account with a stolen password. On shared hosting the server's IP is used by many customers, so one customer's problem affects everyone. And if the IP belongs to a home or office connection, it may be on the Spamhaus PBL, which isn't a penalty: it says that range shouldn't send email directly.

How do I get my IP off a blacklist?

First stop the cause, or you'll be back on within days. Then, in the report you have each list's link to look it up and request removal. Spamhaus and Barracuda have their own forms; SpamCop removes you automatically after 24 hours without new reports; UCEPROTECT, after seven days. No removal should cost you money: if a list charges you to get off sooner, wait for it to expire.

Why don't you say it's clean if it isn't on any list?

Because some list didn't really answer us. Spamhaus doesn't answer every query: depending on where it comes from, it returns an error code (127.255.255.254, for example) or says the name doesn't exist, which is exactly what it answers for a clean IP. To tell the difference we also ask it about 127.0.0.2, which every list includes on purpose. If that one doesn't show up, we know the list isn't answering us and we don't count it as clean.