NNetDiagTools

Bulk Blacklist Checker

Check a list of IPs against major DNS blacklists and export the results as CSV.

Up to 100 entries per job

About this tool

Check many IP addresses against five major DNS blacklists — Spamhaus ZEN, SpamCop, Barracuda, SORBS and UCEPROTECT — in a single background job. Paste IPs one per line or upload a CSV, watch progress live, and export the listed/clean matrix to CSV when the job completes.

Perfect for monitoring a fleet of mail servers, auditing an IP range before purchase, or checking every sending IP of an email service provider after a deliverability incident.

Frequently asked questions

Which blacklists are checked?

Spamhaus ZEN (zen.spamhaus.org), SpamCop (bl.spamcop.net), Barracuda (b.barracudacentral.org), SORBS (dnsbl.sorbs.net) and UCEPROTECT Level 1 (dnsbl-1.uceprotect.net). These cover the lists with the largest real-world deliverability impact.

Are IPv6 addresses supported?

Blacklist checks currently cover IPv4 only, because the major DNSBLs have limited and inconsistent IPv6 coverage. IPv6 entries in your list are reported as skipped.

How fresh are the results?

Each check is a live DNS query against the blacklist itself, so results reflect the list's current state. Brief caching (a few minutes) may apply to repeated checks of the same IP.