Sending an email doesn't require "seeing" anything other than whether the server is willing to receive email for that address though, right? Also, that problem

Sending an email doesn't require "seeing" anything other than whether the server is willing to receive email for that address though, right? Also, that problem occurs due to lack of authorization, not due to authentication failure, right? Authentication failure is a different kind of error to the client—if the server fails to authenticate you, clearly you already know that it's not going to show you anything?