What mail clients do I like? Well, (not counting the web interface to my Yahoo!Mail account) I really only use two with any regularity. Microsoft Outlook at work and Apple's Mail.app at home. I like Mail.app just fine. When I was in college, I used "elm" and "pine." I've even used "mail" enough to not be scared of it.
 First person to identify the pop-culture reference gets a point. It's an easy one. [Edit: The point goes to kimber. The answer is in the comments.]