If you want you can install starship, which provides a lot of the nifty prompt customization I see in other people’s zsh configs. I’ve been using it with bash for a few months now and like it a lot.

I would say white-list instead of black-list if possible.

Beside the point, have you considered the reasons why you might not want to run your own email server in todays age? It’s a fun experience for sure, but if you want it for serious use it’s not for the faint of heart (unfortunately).

Edit: also lol to your friend unknowingly conducting a spam campaign from your server