Glossary
IP Reputation
IP reputation is a trust score mailbox providers assign to a sending IP based on history: bounces, spam complaints, spam trap hits, and blocklist appearances. It affects delivery independently of domain reputation — a bad IP can drag down good domains.
Shared vs dedicated
Shared ESP pools share reputation — dedicated IPs start cold and need warm-up.
FAQ
How is IP reputation different from domain reputation?
IP is tied to the sending machine; domain is tied to From: and auth history.
Can I check IP reputation?
Google Postmaster for Google; blocklist queries; provider dashboards.
Does IPv6 work the same?
Yes — same concepts, ensure PTR and auth for the IP you actually send from.