Thunderbird on the desktop, Aquamail on Android, RoundCube/SquirrelMail via the web in a pinch. Back in the day I also used Evolution on Linux (when T-bird was buggy and lacking some features). Despite having many email buckets in the cloud, I keep no mail in any of them. I've self-hosted since '99, so I've been able to do whatever.

I did use Outlook back in sepia times (pre-'98) and used Pegasus and/or Pine before that. :p