I have expreienced some difficulties regarding UTF-8 encoded text in the subject header. In some clients the encoding is ok, but in others there are obvious something wrong. This occures when sending a mail using a web-form. When I hardcode the text for the subject in the script it works just well. I have also checked the encoding passed by the form with mb_detect_encoding(), and it reports UTF-8. The body seems ok though.
The following headers are sendt simultaneously to the 2 adresses from the same form.