What’s the difference between an IP and a domain blacklist?

IP blacklists list the address your mail is sent from; domain blacklists list domains that appear in messages (the From address and links). A message can be blocked by either, so both are worth checking — they’re maintained separately.

Which blacklist matters most?

Spamhaus, by a wide margin. Its zones are consulted by a large share of mail servers worldwide, so a Spamhaus listing causes broad rejection. Smaller lists like SORBS or Barracuda have narrower reach and less impact.

How do I get removed from a blacklist?

Each list has its own removal page — enter the IP or domain there. Some auto-remove once abuse stops; others need a manual request. Always fix the underlying cause first, or you’ll be relisted quickly.

Why does my IP keep getting relisted?

Because the source of the abuse is still active — usually a compromised mailbox, an abused web form, or an open relay. Delisting treats the symptom; you have to close the source to stay off.

Can I send email from my home IP?

Usually not directly. Residential and dynamic IP ranges sit on Spamhaus PBL by design, so receivers reject direct connections from them. Send through your mail provider’s authenticated SMTP relay instead.

My IP is clean but mail still goes to spam — why?

Reputation isn’t only about the IP. Your From domain or a link domain in the message can be on a domain blacklist, or your SPF/DKIM/DMARC may be missing. Check the domain separately and confirm authentication is in place.

How often should I check?

Right after a deliverability drop, and periodically as hygiene. Listings can appear without warning if an account is compromised, so continuous monitoring beats manual checks for anything you rely on.

Blacklist Check

A blacklist check tells you whether an IP address or domain appears on the DNS blacklists (DNSBLs) that mail servers consult before accepting a message. If your sending IP or domain is listed on a major one like Spamhaus, a large share of your mail gets rejected or filtered to spam. This tool queries dozens of blacklists at once and shows exactly which, if any, have you listed.

How to use it

1
Enter an IP or a domain
An IPv4 like 203.0.113.10 checks the sending IP against IP blacklists; a domain like example.com checks domain-based lists (URIBLs and reputation lists). Not sure which? Check both — they’re listed separately.
2
Read the verdict
Green means no listings on the blacklists we query. Red means at least one hit, with the specific lists named — that’s where you start delisting.
3
Work through each listing
Every blacklist has its own delisting page and its own criteria. Fix the underlying cause first (open relay, compromised account, bad SPF) or you’ll be relisted within days.

How it works

What a blacklist actually is

A DNS blacklist — DNSBL or RBL (Realtime Blackhole List) — is a database of IPs or domains known for sending spam or abuse. It’s published over DNS, so when a mail server receives a connection it can ask, in a single fast lookup, "is 203.0.113.10 on this list?" If the answer is yes, the server can reject the message before it’s even fully received.

There isn’t one blacklist; there are dozens, run by different operators with different rules. Spamhaus is the one that matters most — its SBL, XBL and PBL zones are consulted by a huge share of the world’s mail servers, so a Spamhaus listing hits hard. Others like Barracuda, SORBS, and SpamCop have narrower reach. That’s why a single check across many lists is more useful than testing one at a time.

IP blacklists vs domain blacklists

IP-based lists target the address your mail leaves from. They catch compromised servers, open relays, and IPs in ranges known for abuse — including the dynamic residential ranges on Spamhaus PBL, which is why you can’t send mail directly from a home connection. If you send through a provider like Google Workspace or a relay, the IP that matters is theirs, not yours.

Domain-based lists (URIBLs and reputation lists) work on the domains that appear in a message — the From domain and any links in the body. These catch spam campaigns that rotate IPs but reuse domains. A clean IP with a listed domain still lands in spam, so both halves matter and they’re checked separately here.

Why you get listed

The common causes are boring and fixable: a compromised mailbox blasting spam, a web form or contact page being abused to send mail, an open relay, or a marketing send with a bad list and a spike in complaints. Shared hosting is a frequent culprit — a neighbor on the same IP gets you listed by association.

Reputation is also cumulative. A sudden jump in volume from an IP with no sending history reads as suspicious, which is why "warming up" a new IP gradually matters. And missing authentication feeds into it: mail without SPF, DKIM and DMARC is easier to spoof, so your domain can end up in spam reports you never sent.

Getting delisted (and staying off)

Delisting is per-list. Each operator has a removal page where you enter the IP or domain; some remove automatically once the abuse stops and a cooldown passes, others require a manual request. The critical part is order: fix the cause before you request removal. Delist with the compromised account still sending and you’re back on within a day, and repeated relistings make future removal slower.

After you’re clean, the durable fixes are the usual deliverability basics — lock down authentication (SPF under the 10-lookup limit, DKIM signing, DMARC at least at p=quarantine), close any open relay or abused form, and keep complaint rates low. Monitoring helps: knowing you’re listed within minutes, not when a customer complains, is the difference between a quick fix and a lost week of email.

How to read the results

Result	What it means	What to do
Not listed — green	No hits across the blacklists queried.	Nothing to do. Re-check periodically or set up monitoring.
Listed on 1–2 minor lists — amber	A narrow-reach list flagged you.	Delist and watch — minor lists often auto-remove after the cause is fixed.
Listed on Spamhaus — red	A high-impact listing; expect widespread rejection.	Fix the cause, then use Spamhaus’s removal page. Don’t request removal before fixing.
IP clean, domain listed	Your sending IP is fine but the domain has bad reputation.	Check where the domain appears in spam (links, From) and request domain delisting.