I quite like Outlook as PC email clients go (which all seem pretty crappy if you've ever used Microdot-II or YAM on the Amiga).
One thing that annoys me about it though is that although you can send in Plain Text quite happily, if anyone sends you an HTML email it merrily displays it regardless of what crap it might contain. Any way, decided to Google to see what could be done about it and I came across this little tippette:
http://support.microsoft.com/?id=307594