---
title: "IP Blacklist Checker"
description: "Check if an IP address is listed on major DNS-based blacklists (DNSBL). Test against Spamhaus, SpamCop, Barracuda, SORBS, and more in one real-time blocklist check."
url: https://findutils.com/network/ip-blacklist-checker/
category: network
---

# IP Blacklist Checker

Check if an IP address is listed on major DNS-based blacklists (DNSBL). Test against Spamhaus, SpamCop, Barracuda, SORBS, and more in one real-time blocklist check.

**Use this tool:** [IP Blacklist Checker](https://findutils.com/network/ip-blacklist-checker/)

## Programmatic access

- REST id `ip-blacklist-checker`: POST https://api.findutils.com/api/tools/ip-blacklist-checker/execute (reference: https://findutils.com/api/ip-blacklist-checker/)
- MCP tool `ip_blacklist_checker` on https://mcp.findutils.com (reference: https://findutils.com/mcp/ip-blacklist-checker/)

## Why Check IP Blacklists?

If your IP address is on a blacklist, your emails may be rejected or marked as spam by receiving mail servers. Websites may also block your access. This commonly happens to shared hosting IPs, VPN exit nodes, or IPs that were previously used to send spam. Regular blacklist checks help you maintain your IP reputation and ensure email deliverability.

## Tips for IP Reputation

- Check your IP regularly, especially after setting up a new mail server or changing hosting providers.
- If listed on Spamhaus, resolve the root cause (open relay, compromised account, etc.) before requesting delisting.
- Shared hosting IPs are more likely to be blacklisted due to other users' activities. Consider a dedicated IP for email.
- Set up SPF, DKIM, and DMARC records for your domain to improve email deliverability regardless of blacklist status.
- Some blacklists auto-delist after 24-48 hours if no further abuse is detected. Others require manual delisting requests.

## Frequently Asked Questions

### What is a DNSBL?

A DNS-based Blackhole List (DNSBL) is a database of IP addresses known to send spam or be involved in malicious activity. Mail servers query these lists to decide whether to accept, reject, or flag incoming email.

### Why is my IP blacklisted?

Common reasons include: sending spam (even accidentally), compromised email accounts, open mail relays, malware on your network, or inheriting a previously-abused IP from your hosting provider.

### How do I get delisted?

First, fix the underlying issue. Then visit the blacklist provider's website and submit a delisting request. Most providers have automated forms. Spamhaus, for example, allows self-service removal at their website.

### Does this tool support IPv6?

No. DNSBL is an IPv4-only standard. Most blacklist providers don't maintain IPv6 lists because the address space is too large for traditional DNSBL methods.

### How often should I check?

For mail servers, check weekly. For critical business IPs, set up automated monitoring. After resolving a blacklist incident, check daily until confirmed clean across all lists.

### What leaves my device when I check an IP?

The IP address, once per list. For each of the 12 blacklists the page sends a reverse-DNS query for that IP to Google's DNS-over-HTTPS resolver, which asks the list operator's name server, so Google and each operator see the address. When the page opens it also asks ip.findutils.com for your own IP to prefill the field; that FindUtils service keeps standard request logs.

## Related Tools

- [IP Address Lookup](https://findutils.com/network/ip-address-lookup/)
- [DNS Lookup](https://findutils.com/network/dns-lookup/)
- [DNS & WebRTC Leak Test](https://findutils.com/network/dns-leak-test/)
- [Email Header Analyzer](https://findutils.com/network/email-header-analyzer/)
- [Security Headers Analyzer](https://findutils.com/network/security-headers-analyzer/)