I'm hosting my mail on my own server with postfix and dovecot for 6 years now. It's running smoothly, but I invested alot of work into it. it was fun to figure out how everything is working, anything I needed to know I had to google and stitch the pieces together for my needs, but it was totally worth it because I learned so much when doing it. Since I know how easy the whole system could fail, I would never run a professional/commercial mail server by myself, not even for a small company. Office365, always!

So google for postfix, dovecot, mysql, dkim, roundcube and figure out how to glue it all together. Advise: start with an unused domain, not with your everyday mail address, migration can be done when everything is tested and running.