PHPのmbencodemimeheaderは事前にmbinternalencodingが必要 akiyancom
$mail_from = mb_encode_mimeheader(mb_convert_encoding($mail_from_name,"JIS","auto"),"UTF-7","Q")."<".$mail_from_addr.">";
$mail_from = mb_encode_mimeheader(mb_convert_encoding($mail_from_name,"JIS","auto"),"UTF-7","Q")."<".$mail_from_addr.">";