I've found CLI clients built upon Notmuch are quite nice. Notmuch is an email indexing system. It provides the "full-text search" part. It has an emacs interfa

I've found CLI clients built upon Notmuch are quite nice. Notmuch is an email indexing system. It provides the "full-text search" part. It has an emacs interface and a CLI interface similar to Mutt. If you prefer, it can also integrate with Mutt. To get emails into your machine, use offlineimap or mbsync, which integrate with the above. To send emails, use msmtp, which integrates with the above. This setup has worked well for me for years. Millions of emails can be indexed and searched offline as fast as GMail's search.