IP Blacklist Check

What is a blacklist check?

A blacklist check queries DNS-based blackhole lists (DNSBLs) to determine whether a given IP address has been flagged for spam, abuse, or other malicious activity. Mail servers worldwide use these lists to filter incoming email in real time.

This tool queries multiple well-known blacklists simultaneously and shows you which ones (if any) list the IP. A clean result across all lists suggests the IP has a good reputation for email delivery.

How it works

1. Enter the IPv4 address you want to check and click Check.
2. The tool reverses the IP octets and performs DNS lookups against each blacklist (e.g., 4.3.2.1.zen.spamhaus.org).
3. If a blacklist returns a 127.0.0.x address, the IP is listed. The specific return code indicates the reason category.
4. Results appear as a checklist with green (clean) or red (listed) status for each blacklist.

Blacklists checked

• Spamhaus ZEN: Combines SBL, XBL, and PBL lists — the most widely used blocklist.
• Barracuda: Maintained by Barracuda Networks, used by enterprise email gateways.
• SpamCop: Crowd-sourced reports of spam sources, fast listing and delisting.
• SORBS: Spam and Open Relay Blocking System with multiple sub-lists.
• PSBL, UCEPROTECT, S5H, Mailspike: Additional community and commercial blacklists for broader coverage.