Android

It's paid (one off $15 I think), but has a two week trial but I've been using Nine for a few years now, pretty happy with it.

on desktop I use eM Client. On Android I was using just plain GMail but I saw people in this comment section using other stuff so I checked it out and swapped to FairEmail.

edit: FairEmail is fantastic and I've upgraded to pro. Definitely recommend this one for mobile users with multiple email accounts.

Used to use Thunderbird but I wanted something that just looked like it was from this century. I like how eM Client works and its features and it looks nice. I don't like that I am limited to 2 email accounts though. I'd love something like it that is FOSS and allows more email addresses.

I'm clinging to BlackBerry Hub+ because unfortunately I have not yet found an alternative that does the multi inbox (+ texts, signal, ...) on the same level.

Desktop: Alpine

Android: K-9

Work Desktop: Microsoft Outlook Work Mobile: Microsoft Outlook Home Desktop: mail.google.com Home Mobile: GMail android app

Why? Because I was on Proton personally for a long time but got frustrated with the lack of features and also my wife and I rely heavily on shared groupware stuff like calendars and reminders, so we switched back to Google Mail. Once Proton is a bit more feature-rich, we'll take a look at it again.

Also using outlook. I can say for certain there are some bugs with IMAP email accounts, but other than that it has been working well for me for years.

The only thing I don't like about it (other than the IMAP bugs) is the notification sounds that are exactly the same as my work mail on PC. I get jittery whenever I hear those sounds.

Twobird

I use Em Client on desktop and I love it, on android the Em Client app is still in beta and quite unstable so for now I'm using outlook. Looking at the comments I should give K9 a go.

Edit: Switched to FairEmail for Android

I am with Google Workspace, so most of the time I would use the website, but if I had to use something, it would be Thunderbird on Desktop and Spark on Mobile.

Thunderbird on the desktop; K-9 Mail on Android.

On desktop I stick to the wonderful (for Gnome users, at least) @Geary.

On Android K-9 is fantastic, but regrettably I'm currently using the stock Gmail app because I had trouble setting up my Office365 work email. :(

I manage my e-mails with Blackberry Hub. (On a Fold 4).

It's not amazing, but works well enough.

Protonmail + Duckduckgo's email service, which links to a preexistent email (proton in my case) and allows you to clear trackers from emails and to use randomly generated email adresses.

Edit: only now realized that you asked for client, welp, I use proton's client, but I've been considering using thunderbird lately

Used Eudora long ago. As its support dropped and Qualcomm's development of Thunderbird took off, somewhere during that I embraced the spiritual companion of Firefox. I have to use Outlook at work, that helps me not consider changing at home. Also jumped on the Gmail bandwagon back when you had to get an invite to participate. It was just a side email at the time with storage built in, but when my original ISP provider finally threatened to charge me for having an email account, I moved everything over and linked Thunderbird up to pull from Gmail.

Although my main one is gmail, I have been using proton mail for a while and I'm getting to point where I trust it for most stuff and I will start to move non-critical stuff away from gmail.

I actually swapped to Protonmail last night. Took awhile to change the email address on everything, but worth it. Trying out the free version for now, keeping my Gmail as a backup and for Android.

Tried Fair mail and k-mail and they are ok... Liked Outlook but came back to Gmail since it can't be removed from the device anyways..

Not exactly just a client but a client and a service: HEY from 37signals (formerly Basecamp).

I've been using it for a year and a half and I really love it.