About the IP / Domain Reputation
Sender reputation decides whether mailbox providers trust your mail. It combines blacklist status, reverse DNS, authentication, the age of the domain and third-party signals. This check gathers the indicators that are publicly measurable.
Mailbox providers also use private data such as complaint and engagement rates. Watch Google Postmaster Tools and Microsoft SNDS for those.
Reputation indicators
Reputation combines blacklist status, reverse DNS, authentication and third-party signals. Mailbox providers also use private data (engagement, complaints) that no external tool can see.