Several questions concerning CI4 controller

Sorry for the late reply.
CI and other topics keep me actually busy.

While ago that I played with my mail-server(s).
Yeah, sure in case of running on the same server there should be no need for a certificate at all, agreed.
But why the heck at all configure for TLS?

Need some more nerd stuff here...

What I'd like to know is how CI establishes the connection to the (local) postfix server and how it uses its resources to write out into the web, read mails etc. pp.