Our free IP blacklist check tool scans an IPv4 address against 12 major spam and email blacklists (DNSBLs) to determine if it has been flagged for sending spam, malware, or other abusive traffic. If your IP is blacklisted, it can cause email delivery failures, website access issues, and reputation problems. Run an IP blacklist check regularly to catch listings early and protect your sender reputation.

What Is a Blacklist?

A DNS-based Blackhole List (DNSBL) is a real-time database of IP addresses that have been reported for sending spam, distributing malware, or engaging in other abusive behavior. Mail servers and security services query these blacklists to decide whether to accept, reject, or flag incoming connections. Being listed on even one major blacklist can severely impact your ability to send email — messages may be silently dropped, bounced, or routed to spam folders. Performing an IP blacklist check against these lists is a critical first step in diagnosing email delivery problems.

Blacklists We Check

We check your IP against 12 widely-used blacklists, including:

Spamhaus ZEN: The most widely used blacklist, combining SBL (known spam sources), XBL (exploited hosts), PBL (dynamic IP policy), and CSS (snowshoe spam) lists
Barracuda BRBL: Maintained by Barracuda Networks, used by many enterprise mail filters
SpamCop: Community-driven list based on user spam reports, with automatic expiry
SORBS: Spam and Open Relay Blocking System, covering multiple abuse categories including open proxies and dynamic IPs
Spamhaus DROP: Don’t Route Or Peer — IP blocks that have been hijacked or leased to professional spammers
And several others covering exploits, botnets, and open relays

How DNSBL Lookups Work

Blacklist lookups use DNS as the query mechanism, which is why they’re called DNS-based Blackhole Lists. To check if IP 192.168.1.1 is listed on a DNSBL, the query reverses the IP octets and appends the blacklist’s domain: 1.1.168.192.dnsbl.example.com. If the DNS query returns a result (typically 127.0.0.x), the IP is listed. The specific return code indicates the listing category. This DNS-based approach allows mail servers to perform an IP blacklist check in real-time with minimal latency. The mechanism is formally described in RFC 5782.

Why Run an IP Blacklist Check?

Email deliverability: If your mail server’s IP is blacklisted, your emails may be silently dropped or sent to spam folders without any bounce notification
Website reputation: Blacklisted IPs can trigger security warnings in browsers and antivirus software, scaring away visitors
Shared hosting: On shared servers, another user’s abuse can get the entire server’s IP blacklisted, affecting all sites and email accounts on that server
After a security incident: If your server was compromised, run an IP blacklist check to see whether it was used to send spam during the breach
New server setup: Before deploying a mail server, verify that the assigned IP has a clean reputation from previous users

What to Do If You Are Listed

Identify and fix the root cause — compromised accounts, open relays, malware, or misconfigured software
Visit the blacklist’s website and follow their delisting procedure (most have self-service removal request forms)
Monitor your IP with regular blacklist checks to catch future listings early
Set up SPF, DKIM, and DMARC records to improve your email authentication and prevent spoofing
Review your server’s mail queue for suspicious outbound messages

Preventing Future Listings

Proactive measures help keep your IP off blacklists:

Use strong passwords — Compromised email accounts are a top cause of spam-related blacklisting
Enable rate limiting — Limit outbound email volume to detect abuse early
Keep software updated — Unpatched CMS plugins and web applications are common entry points for attackers who use your server to send spam
Monitor outbound traffic — Set up alerts for unusual email volume or connections to port 25
Use a dedicated IP for email — Separate your mail server IP from your web server to isolate reputation
Schedule periodic checks — Running an automated IP blacklist check on a regular schedule ensures you catch listings before they impact delivery

Related Tools

To find the location and ISP for an IP address, use our IP Geolocation Lookup. To verify your email authentication records (SPF, DKIM, DMARC), try our DNS Lookup with a TXT record query.

IP Blacklist Check