What is “reputation inheritance” between subdomains or IPs?

Reputation inheritance occurs when a new subdomain or IP partially inherits the trust level of its parent domain or neighboring IPs in the same range. This gives new sending identities a starting point rather than forcing them to begin from zero.

A new subdomain like news.tidalmail.com may initially benefit from the established reputation of tidalmail.com. Similarly, a new IP added to an existing pool may inherit some trust from the healthy IPs around it.

However, inheritance is temporary. The new identity quickly begins building its own independent reputation based on its actual sending behavior. Poor performance will erode any inherited trust rapidly.

Inheritance is like a new captain being hired by a respected shipping company. They start with the company's good name, but they must prove themselves through their own voyages. The family name only carries you so far.