I use Thunderbird.

Thunderbird since forever. Before that, Seamonkey and the Mozilla suite.

There are some changes I didn't like over the years like the tabbed interface for everything, but nothing else ever came along that worked as well and was multi-platform.

Thunderbird.

It is the worst email client besides all the alternatives

Betterbird

Thunderbird - on my PC and Mobile... Always worked flawlessly - both with my different mail-services and my own domain name mail server...

Thunderbird. I even use Thunderbird as my RSS reader too.

aerc

Good ol Thunderbird

As a Gnome/GTK enthusiast, I really love Geary. I think it’s the email client that integrates best with the Gnome environment!

seamonkey and thunderbird are both good

Thunderbird and neomutt.

aerc+mbsync+notmuch

If you want a GUI, I was using Evolution before aerc and I was happy with it. I just prefer keyboard navigation which naturally is well supported by any TUI application.

Thunderbird

claws ☞ https://www.claws-mail.org/

I use AERC. TUI that is just so painfully easy to use. integrates with whatever editor you use like vim or emacs or whatever. Account setup is a breeze via a config file thus making it easy to backup. I have it in my nix config so whenever I take my nixos anywhere or reinstall it I instantly have my email ready to go.

How about isync + notmuch + afew + alot + msmtp? gpg decryption not directly supported but using alot's pipeto it can be used to decrypt messages. As using notmuch as indexer it's flow is pretty similar/compatible to/with gmail.

Evolution.

I use FairEmail on phone and Sylpheed on desktop.

Thunderbird

I like evolution a lot

fairmail on phone, postbox on pc

Any halfway decent desktop email client will do the job—people have already listed several. I use claws-mail, but getting it to work with GMail involves the computer equivalent of doing a triple backflip through a hoop, so you may want to go with something more common.

I've tried Vivaldi mail. Might be something for you, but I just didn't like the UI so I'm also still using the web interface for each. Looking forward to seeing others answer as well.

ArcaneChat on mobile

mu4e inside my Emacs session.

Betterbird

Also Thunderbird, but specifically the Betterbird fork.

It works well, its fast, its lightweight (like 100-200MB of RAM), and has lots of features.

I also have my calendar in it.

At this point I'm thinking of creating my own client haha.

I believe MailSpring is really powerful. But some advanced features are behind a pro account. MailSpring itself is open source.

I don't. That's the entire point about having different mailboxes in the first place : they stay isolated and I manage notifications (or not) exactly how I want, when I want.

I use Mailspring. Thunderbird was crashing a lot for me a few months ago but I had used TB for a long time so I will probably move back to it soon.

Kmail on Android, Evolution on laptop.

Evo is a little clunky looking but it integrates calendar, contacts, and does PGP seamlessly using Gnome's key manager.

KMAIL