We're trying to send out HTML emails in multiple languages
(English and Chinese (simplified and traditional)).

The subject as well as the body may contain multi-byte
characters.

We're having trouble making the email readable for all audiences.
 Outlook (back to 2003)
   On English computer
   On Chinese computer
 Hotmail
   on IE with a chinese (simpl or trad) locale
   on Firefox with a chinese (simpl or trad) locale
 Yahoo mail
   on IE with a chinese (simpl or trad) locale
   on Firefox with a chinese (simpl or trad) locale

So far we're base64 encoding with a multipart doc type and
encoding with  Big5 or GB1208 depending on the user's locale.
(UTF-8 didn't work very well).

Is there a mostly-universal way of doing this?

Tara