Kontaktformular mails kommen nicht an!

<?php

$Empfaenger = "****************";

if($_REQUEST['Send'])
{
if(empty($_REQUEST['Name']) || empty($_REQUEST['Email']) || empty($_REQUEST['Nachricht']))
{
echo"Bitte gehen Sie <a href=\"javascript:history.back();\">zurück</a> und füllen Sie alle Felder aus!";
}
else
{
$Mailbetreff = "Kontakt: ";
$Mailbetreff .= $_REQUEST['Betreff'];

$Trenner = md5(uniqid(time()));

$Header = "From: ".$_REQUEST['Email'];
$Header .= "\n";
$Header .= "MIME-Version: 1.0";
$Header .= "\n";
$Header .= "Content-Type: multipart/mixed; boundary=$Trenner";
$Header .= "\n\n";
$Header .= "This is a multi-part message in MIME format";
$Header .= "\n";
$Header .= "--$Trenner";
$Header .= "\n";
$Header .= "Content-Type: text/plain";
$Header .= "\n";
$Header .= "Content-Transfer-Encoding: 8bit";
$Header .= "\n\n";
$Header .= "Sie haben folgende Nachricht erhalten: \n\n";

while(list($Formularfeld, $Wert) = each($_REQUEST))
{
if($Formularfeld != "Send" && $Formularfeld != "Anhang")
{
$Header .= $Formularfeld.": ".$Wert."\n";
}
}

$Header .= "\nDatum/Zeit: ";
$Header .= date("d.m.Y H:i:s");
$Header .= "\n";
$Header .= "--$Trenner";
$Header .= "\n";
$Header .= "Content-Type: ";
$Header .= $_FILES['Anhang']['type'];
$Header .= "; name=";
$Header .= $_FILES['Anhang']['name'];
$Header .= "\n";
$Header .= "Content-Transfer-Encoding: base64";
$Header .= "\n";
$Header .= "Content-Disposition: attachment; filename=";
$Header .= $_FILES['Anhang']['name'];
$Header .= "\n\n";
$Dateiinhalt = fread(fopen($_FILES['Anhang']['tmp_name'], "r"), $_FILES['Anhang']['size']);
$Header .= chunk_split(base64_encode($Dateiinhalt));
$Header .= "\n";
$Header .= "--$Trenner--";

mail($Empfaenger, $Mailbetreff, "", $Header);
echo"Vielen Dank für Ihre eMail!";
}
}
else
{
?>
<table border="0" cellpadding="1" cellspacing="2">
<form action="<?php echo$_SERVER['PHP_SELF']; ?>" enctype="multipart/form-data" method="post">
<tr>
<td>Name:</td>
<td><input name="Name" size="20" type="text"></td>
</tr>
<tr>
<td>eMail:</td>
<td><input name="Email" size="20" type="text"></td>
</tr>
<tr>
<td>Betreff:</td>
<td><select name="Betreff" size="1"><option>Hilfe</option><option>Kritik</option><option>Werbung</option></select></td>
</tr>
<tr>
<td>Nachricht:</td>
<td><textarea cols="25" name="Nachricht" rows="5"></textarea></td>
</tr>
<tr>
<td>Anhang:</td>
<td><input name="Anhang" size="20" type="file"></td>
</tr>
<tr>
<td align="center" colspan="2"><input name="Send" type="submit" value="Abschicken"> <input name="Reset" type="reset" value="Löschen"></td>
</tr>
</form>
</table>
<?php
}

?>

<?php
$pfad= "DATEIPFAD";

$anhang = array();
$anhang["name"] = basename($pfad);
$anhang["size"] = filesize($pfad);
$anhang["data"] = implode("",file($pfad));

if(function_exists("mime_content_type"))
$anhang["type"] = mime_content_type($pfad);
else
$anhang["type"] = "application/octet-stream";


mail_att("email@email.de","Betreff","Hier kannste den Text reinschreiben",$anhang);
?>