Earlier quoted context omitted.
ok but GMail for example has keyboard shortcuts.
Yeah, but I don’t have to learn new shortcuts since I can configure Aerc exactly like I want (and how my mental VIM shortcut model works).
You may not have to learn "new shortcuts" (they're pretty standard), but you're perfectly willing to learn an entire text-based configuration scheme?
VIM has its merits for _editing_ code, but that's not what you're doing with e-mails. You're usually just writing them and sending them off. It doesn't matter if you can save a few keystrokes to, say, change a word a few paragraphs back, and you're not producing structured text in any meaningful way.
It's perfectly fine to like the terminal, but you _have_ to admit it is a preference that has nothing to do with "efficiency".