Linux

Thunderbird.

Betterbird is a fork by a developer who was booted off the project. I've looked at the project and it's literally built on top of drama. It's not a good look, and it does not feel like it's professionally developed.

Evolution is also really really good, but it's a GNOME app. I currently use GNOME and I am not oblivious at how nice the experience of using native apps of it is, but I also know that they don't follow you "well" if you migrate to something else. Make no mistake, Evolution will absolutely run on a KDE desktop, but it won't feel as integrated.

Thunderbird is amazing. It's in active development and it's going through a major visual overhaul / update I really like. It's cross-platform at heart and it looks and works the same on all platforms. It also has the nicest calendar on Linux. Overall, I pick Thunderbird as my client because it's amazing, has a lot of development, has all the features I need and it's made to be cross-platform, so it's not "soft-tied" to any desktop enhancement or GUI toolkit.

I tried "Better"bird for around a month, a year or so ago. Until I hit a bug and submitted a bug report and got this reply:

That's best reported as a Thunderbird issue with exact steps to reproduce.

and later this:

As a first step, we suggest to install the current ESR 91 version of Thunderbird in parallel and see whether the issue exists there.

I personally don't see what's the point of using an email client, if it refers to another email client for submission of some bugs, or if it asks you to install another email client to solve them. I told them and they explained that they're a small team and that

BB is a TB downstream project (fork) and we cannot possibly fix all 14.000 upstream issues.

The turning-point for me was that they simply closed my bug report and, when I told them that that was a let-down, they said:

Users like yourself, who refuse to cooperate or support the project via a donation, are a total let-down indeed, especially if they feel entitled to get a fix.

which was unfair because I do recurring donations to all software I use regularly. But OK, I can simply donate directly to Thunderbird and use that directly.

So I went back to Thunderbird and have been using it without problems since then; they fixed that and other bugs in the meantime. Thunderbird supports all major forms of authentication from what I've seen, so I use it for my work account and other free accounts, all in one.

I wish I remembered more details but the consensus seemed to be to stick with Thunderbird. I use it every day and the new v115 really made it feel new again.

Big fan of Thunderbird. Their recent redesign is neat. You'll have even more reasons in the upcoming month as they will be releasing a mobile app. Basically it will sync deleted and/or already read emails sent to you, really handy

I’m using Thunderbird and it works perfectly fine for me.

Still I also had to configure Evolution as I wanted the Gnome Calendar widget to display my events.

I enjoy using Evolution. I like that you can hack the keybindings and the css theme, and that it works with Microsoft Exchange for mail and calendar sync, required at work.

Proton mail doesn't support email clients unless you pay for and install their Proton Bridge app, FYI.

I've been using Thunderbird since before it was it's own thing, it was packaged as a component of the Mozilla suite IIRC.

I've tried other mail clients like Evolution and KMail, but Thunderbird was the one that never lost me an email message.

Out of all the email clients I've tried, Thunderbird has been the only one that seems to fetch email the instant it comes in, as well as just being all around well featured. I haven't tried Betterbird but from the name I assume it's a fork of Thunderbird so it's probably good as well.

I couldn't yet used to Evolution. Tried it and didn't like it. I really like Thunderbird and donate to them monthly. I've even embraced its RSS reader.

Is it a bit of a RAM-hogging, bloated mess? Yes, but eh, I've got 16 and 32 GB on my two machines. And it has everything I need. Let's me manage 5 or 6 email accounts for different businesses a perfectly.

They are making a lot of changes. We'll see how it ends up in a couple years.

mutt

There is KMail as well

How about Mailspring?

I recently switched back to Evolution from Thunderbird, because the threaded view is more reliable. I miss the good label management and filtering a bit, but is not impossible to use them in Evolution. And Evolution is native to Gnome, which I prefer.

Thunderbird. Not a fan of the new design since it causes dark reader to lag and that means I get flashbanged occasionally. Probably something that will be fixed eventually, but I hate it.

why do people use web clients

Pigeons. E2E encrypted ones if possible.