Glossary · Email
Sender reputation
The running score mailbox providers keep on a sending domain and IP, which decides whether mail reaches the inbox.
Reputation is assembled from bounce rates, complaint rates, spam-trap hits, engagement, and authentication results. It is held per sending IP and per domain, and it is not published: you infer it from where your mail lands.
The practical consequence is that damage is shared. A campaign to a dirty list does not only fail for the bad addresses, it lowers inbox placement for the good ones on the next send.
This is the real economic argument for verification. The cost of a check is small next to the cost of rebuilding a reputation, which takes weeks of careful sending.