PHPMailer character encoding issues

If you are 100% sure $message contain ISO-8859-1 you can use utf8_encode as David says. Otherwise use mb_detect_encoding and mb_convert_encoding on $message.

Also take note that

$mail -> charSet = "UTF-8"; 

Should be replaced by:

$mail->CharSet = "UTF-8";

And placed after the instantiation of the class (after the new). The properties are case sensitive! See the PHPMailer doc fot the list & exact spelling.

Also the default encoding of PHPMailer is 8bit which can be problematic with UTF-8 data. To fix this you can do:

$mail->Encoding = 'base64';

Take note that 'quoted-printable' would probably work too in these cases (and maybe even 'binary'). For more details you can read RFC1341 – Content-Transfer-Encoding Header Field.