Copie cachée

bonjour voici le code demon fichier d'envoi de mail mais la les destinataires voit tous la liste de mes contact je voudrais que les destinataires soit en copie cachée
pouvez vous m'aider

code :

$boundary = "-----=".md5(uniqid(rand()));
$header = "MIME-Version: 1.0\r\n";
$header .= "Content-Type: multipart/mixed; boundary=\"$boundary\"\r\n";
$header .= "\r\n";
if ("$file1" == ''){
$msg = "\r\n";
$msg .= "--$boundary\r\n";
$msg .= "Content-Type: text/plain; charset=\"iso-8859-1\"\r\n";
$msg .= "Content-Transfer-Encoding:8bit\r\n";
$msg .= "\r\n";
$msg .= "$comment\r\n";
$msg .= "\r\n";
}
else{
$msg = "\r\n";
$msg .= "--$boundary\r\n";
$msg .= "Content-Type: text/plain; charset=\"iso-8859-1\"\r\n";
$msg .= "Content-Transfer-Encoding:8bit\r\n";
$msg .= "\r\n";
$msg .= "$comment\r\n";
$msg .= "\r\n";
$file = "$file1";
$fp = fopen($file, "rb");
$attachment = fread($fp, filesize($file));
fclose($fp);
$attachment = chunk_split(base64_encode($attachment));
$msg .= "--$boundary\r\n";
$msg .= "Content-Type: image/gif; name=\"$file\"\r\n";
$msg .= "Content-Transfer-Encoding: base64\r\n";
$msg .= "Content-Disposition: inline; filename=\"attach.gif\"\r\n";
$msg .= "\r\n";
$msg .= $attachment . "\r\n";
$msg .= "\r\n\r\n";
$msg .= "--$boundary--\r\n";
}
$destinataire = "$email";
$expediteur = "[email protected]";
$reponse = $expediteur;
mail( $destinataire, "$sujet", $msg, "nReply-to: $reponse\r\nFrom: $expediteur\r\n".$header);
echo"<center>La Mail a bien été envoyé<br>Merci</center>";
?>
</body>
</html>

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