Yeah, I never thought I'd use a dedicated email client anywhere but work, but Thunderbird is really good.
I also use K-9 on mobile, which I like even more, but marking messages as spam never seems to stick. I still keep getting absolute trash from Google, even though I unsubscribed to updates a long time ago.
I was a K-9 user for a time there. I sprung for the Nine client's 1 time buy for my work email so I could control with a schedule notifications and mail retrieval.
I now use it for my Gmail client so I can add inline photos to my messages on Android.