Mutt, plus a notmuch backend, has excellent search capabilities. Operators meet or exceed what Gmail offers both in terms of speed and features. Neomutt probab

Mutt, plus a notmuch backend, has excellent search capabilities. Operators meet or exceed what Gmail offers both in terms of speed and features. Neomutt probably has better integration. I've never tried because I switched to the Emacs Notmuch MUA package. I find the integration of Emacs packages much better than ncurses CLIs which, unlike non-interactive Unix applications, tend to compose badly. They are little silos. Mutt has an excellent UI design, though. Once learnt, it's really fast to use.