Why do gibberish messages come to The bat and Outlook, but normal to mail services?

Question

PHP

<?
header('Content-Type: text/html; charset=utf-8');
$kuda = '[email protected]';
$zagolovok = 'Сообщение с сайта';
$headers = 'Content-type: text; charset="utf-8"';

if (isset($_POST['ok'])){
  $fio = $_POST['fio'];
  $email = $_POST['email'];
  $tel = $_POST['tel'];
  $text = $_POST['text'];

  $messages = "E-Mail: {$email}\n";
  $messages .= "Номер: {$tel}\n";
  $messages .= "ФИО: {$fio}\n\n";
  $messages .= "{$text}";

  if (mail($kuda, $zagolovok, $messages, $headers)) {
    echo 'Отправлено';
  }
}
?>

Looking ahead, I’ll say that the reconfiguration of the program does not work ...
Thank you in advance for the expert’s practical answer!

Answer 1

$zagolovok = '=?utf-8?B?'.base64_encode('Сообщение с сайта').'?=';
$headers = "Content-type: text/plain; charset=\"utf-8\"\r\n".
           "Content-transfer-encoding: 8bit";

Answer 2

try to replace utf-8 with windows-1251 bkb cp1251 and send something changed?