horde korean charset

[genesisredhat]

can someone help?
I just got a new plesk 7.5 reloaded.
After I setup domains, everything was working fine, except the email.
I cannot read korean language on Horde webmail properly.
I changed the language settings to korean.
But, still. emails from yahoo and hotmail with korean title can not be read. But emails from google and other mails like squirrelmail and neomail with korean charsets works fine.
I don't know where to look at. some emails can be read in korean alright. but some emails cannot. ???

even if I retrieve email to outlook, still the same, I cannot read the title but the text I can read in korean.

I checked the httpd.conf. Seems the korean charset is defined.

what can I do ?

Thanks.

GRH