said email came from. So if I have thousands of servers in a cluster all with the same account that sends email, I would like to know what server that email came from.
Maybe I'm being too simple minded. But my thought is if you want to know something about an email its because you know that email exist, which means you are either looking at the email itself, or a log that the email happened.
If you are looking at the email itself, the headers would tell you which server it came from in the "Received" fields. If you are looking at logs, the postfix logs record the connecting client/server sending the email.
