Thunderbird on PC and K9 on Android. K9 is now a part of Thunderbird and will eventually be rebranded to Thunderbird.
I'm using bluemail on windows,Linux and Android. Not perfect but pretty darn good. Will be interested to see what others say.
Doesn't exist. On Linux I'm using Evolution because Thunderbird is overkill but none of them are great. Or if they are decent they are proprietary.
On Android I was using Spark but got tired of them always pushing the paid features. Plus it was a tad slow to load egg melt and it was quite heavy.
I use the Gmail app with my Gmail and it's simple, light and fast but not great either. It'll do but it's outdated.
If you're on Windows Outlook is one of the better ones. But take a look at Spark, I think it has a Windows app as well as Android. And the design is very nice and clean.
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