How to Check If Your IP Is Blacklisted (And What to Do)

If your emails are landing in spam, one of the first things to check is whether your sending IP — or any IP in your /24 block — is on a blacklist. Different blacklists have different impacts, and the delisting process varies for each.

The Blacklists That Actually Matter

There are 50+ active DNS-based blacklists (RBLs), but most have negligible impact on deliverability. These are the ones that major ISPs actively check:

Blacklist	Severity	Impact	Delisting
Spamhaus SBL	Critical	Gmail, Outlook, Yahoo all check. A listing here means most email is rejected.	Manual request at spamhaus.org/sbl/removal. 2-5 business days.
Spamhaus XBL/CBL	Warning	Indicates compromised host. Many ISPs check.	Auto-delists once abuse stops. Check cbl.abuseat.org.
Spamhaus PBL	Info	Policy listing for dynamic/residential IPs. Not a spam accusation.	Free instant removal at spamhaus.org/pbl/removal.
SpamCop	Warning	Complaint-driven. Some ISPs check.	Auto-expires 24-48h after last complaint.
Barracuda	Warning	Enterprise email gateways check this heavily.	Request at barracudacentral.org/rbl/removal.
SORBS	Low	Minimal real-world impact.	Self-service removal at sorbs.net.
UCEPROTECT	Low	Aggressive listing policy. Most ISPs ignore it.	Auto-expires. Do not pay for removal (they charge for it).
DroneRBL	Warning	Focuses on compromised hosts, proxies.	Request at dronebl.org/rbl_removal.

Spamhaus Return Codes Explained

When you query Spamhaus, the return code tells you exactly what kind of listing it is:

Code	List	Meaning
127.0.0.2	SBL	Direct spam source. This IP sent spam.
127.0.0.3	SBL CSS	Spam support service. IP supports spam operations.
127.0.0.4-7	XBL/CBL	Exploited or compromised host.
127.0.0.9	DROP	Hijacked IP space. Extremely serious.
127.0.0.10-11	PBL	Dynamic/residential range. Not a spam listing.

Why You Should Check Your Entire /24

Checking just your own IP is not enough. If 3 other IPs in your /24 block are on Spamhaus SBL, your deliverability is affected even though your IP is clean. ISPs evaluate at the block level, not just the individual IP.

This is called collateral damage — and it's the reason two identical email campaigns from different IPs can have wildly different inbox rates. The neighborhood matters.

What to Do If You're Listed

Spamhaus SBL (Critical)

Go to spamhaus.org/sbl/removal. You must identify and stop the spam source before requesting removal. Spamhaus will verify. Expect 2-5 business days. Do not send email from this IP until delisted.

SpamCop / Barracuda (Warning)

These are complaint-driven and auto-expire. If you've fixed the issue (unsubscribe links, clean list, no purchased lists), wait 24-48 hours. If persistent, check for a compromised account or forwarding loop.

PBL (Info)

This is not a spam listing. The PBL marks IPs that were previously in dynamic/residential ranges. Free instant removal at spamhaus.org/pbl/removal. Takes 30 seconds.