I just took a look at Mailody 0.2.0 (released yesterday). It is an email client for IMAP only, and a pretty new project, but already some kind of useable. It is pretty fast, much faster than KMail is my impression, and I really like the concept of the compose window:
Having the addressbook and the attach files dialog directly inside the composer window is a pretty cool idea. As well I like, that it can compose only plain text mails, no html stuff… Tabbed mail reading is as well a feature that I like a lot!
It is still in a very early stage of development, but seems very promising! I’ll keep an eye on it! :-)