Been using FOXMAIL email client for a week now, a nifty little piece of freeware, made in China, with self-learning spam filter, only 4M in size. Works well overall, so recommend it. Was using the heavy & cumbersome Outlook. Transferring address book worked a treat, but no solution for transferring email (MS's fault actually, as PST format is not widely documented.) apart from manually doing it.
I used that for a few weeks until my computer died and I didn't reinstall it. Found it to be nice and simple although it wasn't designed in the way I would use it (i.e. the password protected mailboxes, I would've replaced with profiles
I'm using PocoMail now...it has skinning support which is always a plus when you want things looking pretty. Works pretty much like Outlook apart from the bonus of being non-Microsoft
There was another email client called Eudora which I downloaded which had good spam support, but the decent version cost money and the GUI was pretty ugly, lol.