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Blacklist / DNSBL Check

Check if an IP address appears on major DNS-based blacklists (DNSBL). Detect if your mail server is blacklisted.

Frequently Asked Questions

Common questions about the Blacklist / DNSBL Check tool.

A DNS-based blocklist of IPs (and sometimes domains) known to send spam, phishing, or malware. Mail servers query DNSBLs on every inbound connection to reject bad IPs before accepting the message.

Common causes: (1) malware on a machine in your network using SMTP, (2) open relay, (3) compromised mailbox credentials, (4) legitimate-but-unwanted bulk mail, (5) shared hosting neighbour was the real culprit.

Find and fix the root cause (patch, rotate creds, block outbound SMTP from non-mail servers). Then submit a delisting request on the DNSBL's site. Spamhaus, Barracuda, and SORBS all have self-service portals.

No. Spamhaus, Barracuda, and SpamCop are widely respected. Smaller DNSBLs can be noisy or outdated. If only one obscure list flags you, most major mail servers won't block you.

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