I am looking to self host emails for a small non profit organization. MX plans are cheap when buying a domain name but come with poor webmail like Roundcube[0] which really feels outdated when compared with Gmail or Fastmail. I am looking to self host a full featured modern webmail client but can’t find any. Why ?
Soho[1] is the best I have found and supported by Gandi[2].
[0] https://github.com/roundcube/roundcubemail [1] https://github.com/inverse-inc/sogo [2] https://webmail.gandi.net/SOGo/
I hope you don't mind, but i read about your france project a few days ago and would love to get in contact with you on your experience about it.
Nothing big more like your experieince, things like how easy is it to build your things in france, water rights, internet etc.
My email is sicaine at gmail com
Why not use something like Postfix or Exim with a local application like Thunderbird?
Also unless this is a tech-savvy organization or emailing or FOSS is part of their mission, consider just sticking with something from Google, Microsoft or Fastmail. A shelter for homeless kittens probably doesn't want to mess with something custom.
It's not as easy as you imagine, especially when you want to make it "simple" like Gmail, there's a lot of work that goes into a "simple for the user" interface.
This doesn't really answer your question about why there aren't many options, but: did you find mailpile[1] on your travels? It could be worth considering too.
[1] - https://www.mailpile.is/