[imp] How to disables to UTF-8 Viewing !

[Umut Arus]

Hi,

I'm using webmail version of IMP: H3 (4.1.4) and Horde: 3.1.4.
Sending message as ISO-8859-9 translates to UTF-8 in IMP. In other 
words, browsers are changing its "Character Encoding" to UTF-8 although 
message source is "Content-Type: text/plain; charset=ISO-8859-9; 
format=flowed
Content-Transfer-Encoding: 8bit"

Why is it translates?

Is there an option? Can I change this option?

Regards,