The first thing which put me off after logging in to the kubuntu (9.10) desktop for the first time was the fonts. They are two problems I have with the default Kubuntu fonts (Well the first one is not much of a problem but personal taste.)
1: The default fonts The default font setup on Kubuntu Karmic is ok. But I wanted some better than ok, so I install the liberation fonts which has always served me well in the past (especially when I was a gnomie 
) It comes as part of the Kubuntu-restricted-extra package.
You can install as a standalone package by clicking 
It can always install the package from terminal
sudo apt-get install ttf-liberation
) hence i find thunderbird to be the email client that just suits my needs. It doesn’t try to take over the world or make dinner for me. Its first and foremost an email client and its keeps with the Unix philosophy of do one thing and do it well.