I’m self-hosting my mail server for all kinds of neat tricks, like turning mailing lists into RSS feeds and putting attached bills in the right folder. But it is tricky to pull off, because 90% of all email is spam so you must take that seriously because otherwise nobody will accept you mail. One thing I learned quickly is not to use PGP. They almost always and up in spam boxes.
I switched from radicale to baikal because vdirsyncer (which I then used) didn’t agree with radicale on the caldav standard. And I’m very happy with Filestash. It’s fast and does the only thing I need it do do, stash files.
BTW I used to use NextCloud, but that was way too much work and I really like tools that do just one thing and do it well.