Worth noting that if you like the idea of indexing your mail, there's also Notmuch. It's a dedicated email search and indexing tool and is very nice when paired with something like OfflineIMAP to sync messages.
What I really want is: mutt's UI, but with a SQLite3/PostgreSQL backend, and mutt not to iterate a mailbox when opening it, and an async IMAP client that reconnects as needed.
Similar concept and similar speed, but notmuch is a little more actively developed. I also find the notmuch command line interface a bit easier and the various tools built on top of it to be better. Alot, the terminal UI I mentioned in the parent comment, is almost exactly what I want in a mail program.
https://notmuchmail.org