A DNS-based blocklist (DNSBL, also called an RBL) is a list of IP addresses with a poor sending reputation. Mail servers query these lists to decide whether to accept mail. Being listed can cause your email to be rejected or marked as spam.

Why might my IP be listed?

Common reasons: a compromised account sending spam, a misconfigured mail server, shared hosting with a bad neighbour, or a past incident. Each blocklist publishes a delisting process.

Can I monitor this automatically?

Yes. Uptimeify’s DNSBL monitoring checks your IPs against blocklists on a schedule and alerts you the moment one gets listed, so you can act before deliverability suffers.

DNSBL / Blacklist Check

Check a public IP address (IPv4 or IPv6) against the blocklists our DNSBL monitoring uses: with the reason and a delisting link for every listing.

Enter a public IP address to check.

This check works inside your AI agent, too.

You are running by hand what Claude, Cursor or ChatGPT could do for you directly. Uptimeify offers this and 19 more checks as an MCP server: SSL, DNS, email authentication and more, right in your workflow. No account, no API key, on EU infrastructure.

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Frequently asked questions about DNSBL / Blacklist Check

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