For those who want to get their hands dirty, here is a full, step by step tutorial to set up your own email server: https://www.linuxbabe.com/mail-server/setup-basic-postfix-ma...
migadu's mail number limit does not make sense to me: This risks losing emails.
That guide is all very well but it is very complicated to follow and setup, and I have been using Linux for a reasonable amount of time (10+ years).
I was surprised that there wasn't an open source script, a bit like you would run with apt-get, that would simply ask you some questions and do all the bits for you.
Postfix is obviously really powerful but for a noob to it, I found it overwhelming without consulting lots of docs.
I did find https://www.iredmail.org/ but that has a feature limit for the free version. The bits you actually really want costs up to $500/year. Not much if it is for your main business, but a lot when you only want it for a part of your larger system.
Try out this [0] , it’s pretty easy to self host , comes with decent defaults and makes it quite easy to setup a bunch of tools from spam checking to anti virus , dkim , dmarc , etc and gives you some handy parameters you can change in its default config file after that you can further customise the tools it uses directly (although I’ve only had to do that once or twice while setting up some custom settings) Takes 5 mins to setup a decent instance