the question of simplicity seems to be rather complex :D
I personally always go for bash if I want something simple tecmint.com/best-commandline-email-clients-for-li…
but they mainly don't have less features they have a different learning approach since you often cannot use a mouse and this forces the UI design to work in a different way.
Did you mean something like that?
edit:
oh and your english is fine ... i even would dare say you write way better english than I do :)