Asagidaki charsetlerden birini kullanmayi denedin mi?
Content-Type: text/html; charset=koi8-r
Content-Type: text/html; charset=windows-1251
Content-Type: text/html; charset=x-mac-cyrillic
Content-Type: text/html; charset=cp866
Content-Type: text/html; charset=iso-8859-5