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Blacklist & DNSA free tool by NullFortis
Blacklist Checker
Is your IP or domain listed?
What is it?
DNS-based blacklists (DNSBLs) track IP addresses known for sending spam or abuse; mail arriving from a listed IP is dropped or spam-foldered by many receivers, regardless of how well-authenticated it is otherwise.
Why it matters
SPF, DKIM, and DMARC can all pass perfectly and your mail can still land in spam if the sending IP itself has a bad reputation.
Impact if ignored
A listing on even one major blacklist can quietly tank inbox placement — usually with no error message at all, just a much lower response rate.
Common use cases
- Check a new sending IP before switching to it
- Investigate a sudden, unexplained deliverability drop
- Monitor a shared IP or ESP's ongoing reputation