normalize_charset

[yblin]

Hi! I've encountered a problem.I want to filter Chinese spams，and 
through some documents I know that SpamAssassin can transform non-UTF-8 
encoding emails into UTF-8 encoding ones.So I think that SpamAssassin 
can filter not only UTF-8 encoding emails but also non-UTF-8 encoding 
emails if I enable the option "normalize_charset".However,when I use 
this option, a strange problem occures---I can not filter UTF-8 encoding 
or non-UTF-8 encoding emails with this option enabled but can filter 
UTF-8 encoding emails with this option disabled.
Could you tell me what the problem is and how to solve it?