autoresponder and cyrillic text issues

[timur@]

Hi!
We are using plesk 8.6.0 for Linux and we've faced with some problems setting up autoresponder: it works ok, however all cyrillic texts in auto-reply messages are garbaged and replaced with ??????????? symbols.
We've tried with koi8/utf8/windows-1251 encondings, plain and html, but that didn't help.
Can anyone suggest what to do to solve this problem?

Thanks.