01 · Allocation
The block it belongs to
The range this address was allocated in, and the registry that issued it.
02 · Location
Where it is registered
The country on the allocation record.
03 · Contacts
Who to talk to
The organisation on record, and where to report abuse from this address.
04 · Routing
Who announces it
The autonomous system carrying this address on the public internet.
05 · Reverse DNS
What it calls itself
Mail servers are judged on this. A missing or mismatched record is a common reason legitimate mail gets filtered.