@YurkshireLad I would like to share my thoughts as I have been asking myself the very same question.
My initial motivation has been to de-google and to become more privacy-conscious. Following the well-known line "When something is "for free" you become the product" I've looked at many commercial solutions, that advertise to be privacy focussed: Mailfence, mailbox.org, Tutanota, ProtonMail, to just name a view. Those are all fine choices.
Then I wanted to learn more about what's out there in the FOSS space and came across:
The below referenced site taught me the "ins and outs" in detail and I really got my teeth into things:
I came to realize that self-administering a mail server is too much for me.
In looking at many of the before mentioned "out of the box" solutions like MailCow, iRedMail, Mail-in-a-box, etc. I finally settled with Cloudron for my e-mail needs.
For me, this is an excellent choice. And while Cloudron does not position itself as a Mail Server solution, it is surprisingly well done. Really well done.
The interface to set up users, aliases, mail-domains, etc is slick, simple, yet powerful. The backup solution is well established. And the whole thing is integrated into so much more than just e-mail.
I am not only very happy, but also convinced that I have the best solution that meets my needs.
I can - from personal experience - highly recommend giving this solution a very hard look.