Setup an Email server [closed]

I know that the title of this post is not very indicative. But I thought the simpler it was the more people would watch.

I am trying to set up a mail server with Ubuntu 20.04. The software I am using are: Dovecot, Postfix and Fetchmail. The machine where I work is running webmin which allows me to access the server management directly from the browser. Returning to the main problem, I would like to ask you if anyone has any advice for configuring the 3 software. Should I first configure Postfix, then Dovecot and finally fatchmail or is it better to start from something else?

Maybe you could get inspiration from that: Mail-in-a-Box