Seeing this caused me to see whatever happened to Pegasus Mail and it turns out it is still be actively maintained thirty years after its initial release (!) - https://www.pmail.com/
I loved that thing so much when I was a teenager.
Wow, this is a trip down memory lane! I remember using this way back in my early university days. I miss the days of desktop native email clients. I keep trying them but keep going back to the web apps because it seems all of the features are there.