Email Blacklist Checker

Email Blacklist Checker queries selected DNS-based blocklist zones for an email-sending IPv4 address or domain. It uses DNS-over-HTTPS to make the lookup from your browser and presents each zone as listed, not listed, or unavailable, so you can investigate sender-reputation issues with more context.

DNSBLs are only one input into email delivery. Major mailbox providers also evaluate domain authentication, IP and domain reputation, recipient engagement, complaint rates, sending behavior, and content. Use this tool to identify potential DNSBL concerns, then follow the listing operator’s documentation before attempting remediation.

• IPv4 and domain queries: Check a sending IP address or domain against selected DNSBL-style zones.
• DNS-over-HTTPS lookup: Uses a public DNS resolver from your browser rather than a server-side proxy.
• Transparent status: Distinguishes a positive listing from a clean response and an unavailable lookup.
• Reverse-IP query generation: Shows the standard reversed IPv4 format used by many DNSBLs.
• Practical remediation guidance: Explains what to investigate when a listing appears.
• No stored input: The tool does not retain the domain or IP you check.

1. Enter the sending IPv4 address or sending domain used by your mail infrastructure.
2. Choose IP or domain lookup and run the check.
3. Review each DNSBL status. “Unavailable” means the browser resolver could not give a definitive answer.
4. Investigate any listed result through the DNSBL operator’s official website and policy page.
5. Fix the root cause such as compromised infrastructure, list-quality issues, or unwanted mail, then request delisting only where appropriate.

IP example: For 192.0.2.25, many IP DNSBLs use the query 25.2.0.192.zone.example. The checker creates that reversed form automatically.

Domain example: A sender checks mail.example.com against a domain-capable reputation zone. Results can differ from its outbound IP reputation.

Unavailable example: A zone returns no public answer through the resolver. Treat that as unknown, not as proof that the sender is not listed.

• Diagnose reputation issues faster: Start investigating delivery problems with concrete DNSBL evidence.
• Avoid false certainty: See unavailable queries separately from clean results.
• Support healthier sending: Combine DNSBL checks with authentication, consent, and engagement monitoring.
• Reduce manual lookup work: Query multiple selected zones in one interface.
• Keep control of the lookup: Run browser-based checks without creating an account.