IP Reputation Lookup
Check an IP address against reputation signals and blocklists, and understand why an address gets listed and how to get it delisted.
Last reviewed by the Radiatus Cloud team
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What reputation actually measures
IP reputation is an aggregate judgement built from observed behaviour: spam sent to trap addresses, connections to known command-and-control infrastructure, credential-stuffing attempts, and reports submitted by other operators. It is a statistical signal about an address, not a verdict about the person using it, and it changes over time as behaviour changes.
Shared addresses and inherited reputation
The most common reason a legitimate sender finds itself listed is that the address is shared. Residential connections behind carrier-grade NAT put thousands of subscribers on one public address. Cloud providers recycle addresses between customers, so a newly allocated IP may carry the history of whoever held it last. If you have just provisioned a server and outbound mail is being rejected, check the address history before assuming your own configuration is at fault.
Blocklists differ enormously
Well-run lists such as Spamhaus have clear listing criteria and a functioning delisting process. Others list aggressively, never expire entries, and have no realistic appeal route. Being on one obscure list means very little; being on Spamhaus means your mail is being rejected at a large fraction of receivers. Weight the lists rather than counting them.
Getting delisted
Fix the cause first, because delisting without fixing anything results in relisting within days and repeated requests are treated less sympathetically. Find the compromised account, the misconfigured relay or the infected host. Then submit the delisting request through the list's own process, describing what was wrong and what you changed. Most reputable lists remove promptly once the underlying issue is genuinely resolved.
Sending mail from a new address
A new IP has no reputation, which is not the same as good reputation; receivers treat unknown senders cautiously. Warm up by increasing volume gradually over several weeks rather than sending a large campaign on day one. Publish SPF, DKIM and DMARC records before sending anything, keep bounce rates low, and remove unengaged recipients. Sender reputation now depends more on domain authentication and engagement than on the IP alone.
Related tools
- Port Scanner — Check which common ports respond on a host and understand what each exposed service means. Scan only systems you are authorised to test.
- DNS Misconfiguration — Analyze DNS records (TXT, SPF) for security gaps.
- TLS Compat Tester — Check client-server compatibility for TLS versions.
- Firewall Rule Risk — Evaluate firewall rules for over-permissive exposure.
Frequently Asked Questions
Why is my IP on a blocklist when I have done nothing wrong?
Usually shared history. Residential connections sit behind carrier-grade NAT with thousands of others, and cloud providers recycle addresses between customers, so you may have inherited a previous tenant's reputation.
How do I get an IP delisted?
Fix the underlying cause first, then submit a request through the list's own process explaining what was wrong and what changed. Delisting without fixing anything leads to relisting within days and to less sympathetic treatment.
Are all blocklists equally important?
No. Spamhaus and a handful of others are used by a large share of receivers and matter a great deal. Many small lists have aggressive criteria, no expiry and no appeal route, and being on one has little practical effect.
Does IP reputation still matter for email?
Yes, but less than it did. Domain reputation, SPF, DKIM and DMARC alignment, and recipient engagement now carry more weight. A clean IP with no authentication will still land in spam.
How should I warm up a new sending IP?
Increase volume gradually over several weeks rather than sending a large campaign immediately. Publish SPF, DKIM and DMARC before the first send, keep bounces low, and drop unengaged recipients early.
Privacy & Security
Lookup done locally.
About This Tool
This tool runs entirely in your browser. No data is sent to any server, ensuring complete privacy. Simply use the interface above to get started — no registration or login required.
Disclaimer: This tool is provided "as is" without warranty of any kind. Results are for educational and utility purposes.
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NetworkCheck which common ports respond on a host and understand what each exposed service means. Scan only systems you are authorised to test.
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NetworkAnalyze DNS records (TXT, SPF) for security gaps.
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NetworkCheck client-server compatibility for TLS versions.