[exim] setting character set in exim filters \ mail

Hello,

I am reading the documentation for filters in exim. I had no problem
setting up a simple filter but now (apart from the multipart/alternative
format) I am interested to hear if I can set the character set so that the
email being generated in response to some conditions, can make use of the
UTF-8 encoding.

I thought I could use

headers charset "UTF-8"

but exim complained when the filter had such a line. How should I set the
characterset?

If UTF-8 can't be used, then can I use the character set of the incoming
message and use mail function to automatically replay in the same
encoding? Can someone please clarify? I am in doubt and yet I need UTF-8
because I will have to handle languages like Chinese, Russian, etc.

Thank you!

--
Zbigniew Szalbot