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Inbox Theory

Deliverability

ASN Lookup

Resolves the Autonomous System (AS) that currently announces an IP address — who actually operates it, via Team Cymru's free DNS-based service.

Every IP address on the internet is announced by an Autonomous System (AS) — a network operator's own routing domain. Knowing which one an IP belongs to helps identify who actually operates it, useful when the reverse DNS hostname alone isn't conclusive. IPv6 isn't supported yet.