$to = '[email protected]';
$subj = "Тема...";
$subj = base64_encode($subj);
$subject = "=?windows-1251?B?".$subj."?=";
$headers = "MIME-Version: 1.0\r\n";
$headers .= "Content-type: text/html; charset=windows-1251\r\n";
$message = "Текст";
mail($to, $subject, $message, $headers);