IP Reputation Lookup

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.