Alpine (née PINE) is an excellent console mail client. Very good IMAP support (the code underneath is from the reference implementation for IMAP). It's interactive, with menus and prompts, so it's easy both to configure and use. However, it's also powerful. It has a query language for searching your email according to various attributes (including "tags" you can apply to your email), and you can refine queries with further queries.
When GMail came along and everyone went "Ooh, powerful email searching!" I, and other PINE/Alpine users were wondering "uhm, we have that already?".