Ask HN: Email client that threads by sender, IM-style?

Does anyone know of an email client that groups emails by sender like IM?

The UI would be a list of sender names ordered by latest message with a preview of latest email under them, and then clicking on that would reveal all the emails by sender threaded by subject?

This seems like such a superior interface especially for regular senders, yet there doesn’t seem to be any clients that support this. I’m kind of baffled honestly considering how popular this UI is for chat apps.