What Is an IP Blacklist?
An IP blacklist (also called a DNSBL — DNS-based Blackhole List) is a real-time database of IP addresses known to send spam, host malware, conduct abuse, or engage in other malicious behaviour. Email servers query these lists before accepting incoming mail and reject or flag messages from listed IPs.
Check your IP now: IP Blacklist Checker →
How DNSBL Blacklists Work
When your mail server sends an email, the receiving server performs a DNS lookup: it takes your IP address, reverses it, and appends the blacklist domain. If a DNS record exists, your IP is listed and the email is rejected or marked as spam.
For example, to check if 1.2.3.4 is in Spamhaus ZEN: the lookup is 4.3.2.1.zen.spamhaus.org. Our checker does this for 20 major blacklists simultaneously.
Major Blacklists We Check
- Spamhaus ZEN — The most widely used blacklist. Combines SBL, XBL, and PBL. Blocking by Spamhaus affects deliverability to almost all major email providers.
- SpamCop — User-reported spam blacklist. IPs are listed when multiple users report spam from them.
- Barracuda — Used by Barracuda email gateways, common in enterprise environments.
- SORBS — Multi-category blacklist covering spam, proxies, dialup ranges and more.
- UCEProtect — Three levels: L1 (single IP), L2 (network /24), L3 (entire ASN).
- CBL Abuseat — Detects IPs sending spam via botnets and malware.
Why Is My IP Blacklisted?
- Your IP sent spam — Either your server was compromised or a misconfigured application sent spam
- Malware on your network — A device on your network had a botnet infection sending spam without your knowledge
- Shared IP with spammer — Dynamic ISP IPs are frequently reassigned. A previous user of your IP may have been a spammer.
- Open mail relay — Your mail server accepted and forwarded email from any sender (misconfiguration)
- Spam trap hits — Your mailing list contained old or purchased addresses that are now spam traps
How to Get Your IP Removed From Blacklists
Step 1: Fix the Underlying Issue
Blacklists will relist you immediately if you request removal without fixing the root cause. Scan your network for malware, check your mail server logs for unusual activity, and verify your mail server is not an open relay.
Step 2: Spamhaus Removal
- PBL (Policy Block List) — For residential/dynamic IPs. Automatic self-service removal at spamhaus.org/pbl
- SBL (Spam Block List) — Manual review required. Submit evidence you have fixed the spam source.
- XBL (Exploits Block List) — Automatic removal once your IP stops sending botnet traffic (usually 24–48 hours after cleaning)
Step 3: SpamCop Removal
SpamCop listings expire automatically after 24 hours if no new spam is reported from your IP. You cannot manually request removal — just stop the spam source.
Step 4: Barracuda Removal
Visit barracudacentral.org/rbl/removal-request and submit a removal request. Barracuda reviews within 12 hours.
Related Tools
- What Is My IP — See your current IP and full connection details
- Email Breach Checker — Check if your email was in a data breach
- DNS Leak Test — Check if your VPN is leaking DNS queries
