The state of gui linux email clients has been abysmal for years. My primary usage mode is across multiple imap accounts with a decade of email and probably 15Gb total..

Evolution - imo bloated, painful, and abandoned. Thunderbird - Less bloat, but not really progressing.

Opera's m2 email client was probably the best i could find for significant volume though closed source.

The cli clients are significantly better mutt + notmuch, and sup were my favorites.

I finally just went down the gmail road..

Beauty and features are great, usability at volume is even better. Good luck to yorba folks.