Same for me. I'm a die-hard Thunderbird fan (it's ugly but it works lol).
Used to use TB at work until we switched to Google Workspace and they globally disabled IMAP access. Now I'm stuck with webmail and my productivity went to absolute shit.
Yeah, I mostly use Thunderbird and FairEmail but it's nice to have a backup when I'm in places I can't use those, or can't be bothered setting up a new client.
Whelp, nextcloud isn't known for being fast. I don't have hundreds of thousands of emails yet so I can't comment on that, but one thing for sure is as you put more and more data on it, you'll have to add more CPU and RAM to it or it'll getting more and more sluggish.
NC Webmail UI is poorly designed: compose window is just a small box on the center of the screen, there’s no way to have the markup tools permanently show up;
NC Webmail UI is broken: if you select a bunch of text and turn it into a bullet list, the bullets won’t even show up on NC, other e-mail clients will see them tho;
Integration/SSO with IMAP is cumbersome: not well documented, default configuration doesn’t even handle a simple “login with the email email and password as the IMAP account” type of setup that is commonly expected;
WebUI is slow and fails often: if you open the browser console you’ll find lots of warnings and errors.
I do have a lot of complaints related to mail but if NC is any kind of useful replacement for MS365 / Google Workplace a decently working webmail is the bare minimum. RoundCube is WAY better than what NC is currently offering.
I finally have my email set up with Thunderbird (and K-9 on my phone) so that I have mail and calendar stuff in one place and don't use my browser for every old thing. Before that I was a brainwashed Google zombie for quite some years and used only Google webmail. It took so long to get rid of all their stuff.
Roundcube always! I tried others and always went back to Roundcube. If you install it properly (using composer for everything) it won't break on updates.
@EinfachUnersetzlich@lemm.ee I loved rain loop until I learned they had a vulnerability where a malicious email could compromise the system. IDK if they have fixed it but it was my favorite webmail by far. Nowadays I'm using desktop clients sadly.