Pro move: type dmarc:yourdomain.com or blacklist:1.2.3.4 straight into the box — it switches tools for you.
About this tool. Every IP address belongs to a block allocated by a regional registry (ARIN, RIPE, APNIC…). This lookup shows the owning organization, the block's range and name, and where it's registered — useful for abuse reports and for knowing who's really behind a server.