Flash-based email form using PHP (trouble sending chinese)

I am new to PHP so I followed the tutorial on this website to build a flash form using PHP. This works well with English, but doesn’t send chinese characters. It doesn’t display chinese in the microsoft outlook. How do I fix this matter?

One note is that I’m able to read the email in chinese using Mac Entourage when I choose the UTF-8 encoding, it even displays in hotmail. Problem right now is it doesn’t display in outlook on a PC.

Is it related to changing the default character set to UTF-8 in PHP? or enabling the mbstring for chinese support? Or simply just the outlook problem?

Would be great if anyone could direct me to the right direction. Thanks