I haven't researched Notmuch, but I've heard some interesting things about it. I used to use Mutt back in the day. Whatever I use would have to have Org integration, though.
Tbh, I just haven't researched other things and I haven't had the time. But Gnus does seem to fit well how I organize my mail: I subscribe to a lot of mailing lists, each of which are filtered into their own folders via Sieve scripts, before they touch my MUA. I also organize normal mail similarly.
This is a late reply, but thanks for your input. I'll look into them further. What interests me is your replacing Dovecot + Sieve with your MUA; I'll have to see if I want to do that or not.
No worries. For some time, before fully transitioning to Notmuch as a MUA, I was running Gnus with just Notmuch (using nnir notmuch search backend). So no Dovecot or Sieve. A pure Maildir.
I'm not sure whether you'd loose any feature like this, I don't think I did. But perhaps it's much simpler and quicker to switch to Notmuch for Emacs.
Tbh, I just haven't researched other things and I haven't had the time. But Gnus does seem to fit well how I organize my mail: I subscribe to a lot of mailing lists, each of which are filtered into their own folders via Sieve scripts, before they touch my MUA. I also organize normal mail similarly.