Maybe dodo[1] is something for you. It is basically a graphical email client but with lots of vim-bindings.

Basically the best of both worlds, terminal and graphical. Like the qutebrowser[2] for emails.

However I think its kinda in a unmaintained state and only supports notmuch backend.

1: https://github.com/akissinger/dodo 2: https://qutebrowser.org/