WhatIP tool
Check IP reputation and common blacklist signals, including a Spamhaus signal when available.
Example:
Results will appear here.
What you should know
A blacklist (or reputation) check looks up an IP address against databases that track addresses associated with spam, malware, abuse, or other unwanted activity. It is most often used to check whether a mail server's outgoing IP has been flagged, which can cause legitimate email to land in spam folders or be rejected outright.
A listing means that specific database has recorded activity it associates with abuse from that address at some point -- it does not automatically mean the current operator is at fault, since IP addresses are reassigned between customers over time, especially on shared hosting and residential ISP pools. Reputation lists differ from each other, so being flagged on one and clean on another is common.
Most reputable blacklists publish a delisting process once the underlying issue -- an infected device, a misconfigured mail server, or a previous owner's activity -- has been resolved. Checking here first confirms whether there is actually a problem to fix before you go further.