QMAIL!
http://q3.snak.org/en/
It reminds me of Mozilla Thunderbird. I was using it for quite a while. It will intergrate with your current contacts and you can also set it to check mail ever X mins, whatever you want X to be. You have to read the directions because there are so many options it's not obvious, at least it wasn't to me, which ones you need to select for those two. It's actually a very easy and nice program that supports displaying your email in HTML!!!