The In fact, the above diagram above doesn't even does not include reading emailmail messages, but it's as simple this acts as it gets (if you want a starting point in order to run an a basic email server). You will need to learn to administer basics of all the systems in the diagram. We won't go in too much depth, only the minimum you need. But we will not (for example) go over every detail of Postfix, which on its own has a rather [https://en.wikipedia.org/wiki/Postfix_%28software%29#Architecture complex] [https://www.credativ.de/blog/postfix-architecture-overview diagram].