Database issue

Hello everybody,
I have written some php script for mail confirmation script,After data inserted in to table the auto increment column value have to sent to customer along with confirmation mail. I have getting output for data insertion in table,confirmation mail but I didn't get the auto increment column value in the mail. Please see my code below.

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$to = "sales@harvam.in";
 $subject = "Contact Us";
 $email = $_REQUEST['email'] ;
 $message = $_REQUEST['msg'] ;
 $quantity = "/Quantity " . $_REQUEST['quantity'] ;
 $path = "/Upload: " . $_FILES["file"]["name"];
 $message = $message . $path . $quantity;
 $headers = "From: $email";

$sent = mail($to, $subject, $message, $headers, $quantity) ;
 if($sent)
 {print "Your mail was sent successfully";
 }
 else
 {print "We encountered an error sending your mail"; }



                                                          //for confirmation mail


$to =  $_POST['od_email'];
$subject = 'Order Confirmation From Harvam Enterprises| : '.  $_SESSION['orderno.'] ;
$hostname = "localhost";
$db_user = "*********";
$db_password = "**********";
$db_table = "*********";
$database = "*********";
$db = mysql_connect($hostname, $db_user, $db_password);
mysql_select_db($database,$db);
if (isset($_REQUEST['send'])) {
 

                                          //for getting auto increment column value from database and then sent to customer along with confirmation mail

 
$ordersql = "SELECT MAX(orderno.) FROM hvm_order";
if($result = mysql_query($ordersql ,$db))
{
echo 'Your order number sent to your mail<br><br>';
}
else {
echo "ERROR: ".mysql_error();
}
}

$message = 'order confirmation from harvam(Make your own gift).You will get your order number shortly' . $result ; 

$from = "sales@harvam.in";
$headers .= 'To: ' .$to. "\r\n";
$headers .= 'From: ' .$from. "\r\n";
$mail_sent = @mail( $email, $subject, $message, $headers);
$headers  = 'MIME-Version: 1.0' . "\r\n";
$headers .= 'Content-type: text/html; charset=iso-8859-1' . "\r\n";

if ($_FILES["file"]["error"] > 0)
  {
  echo "Error: " . $_FILES["file"]["error"] . "<br />";
  }
else
  {

  }


if ((($_FILES["file"]["type"] == "image/gif")
|| ($_FILES["file"]["type"] == "image/jpeg")
|| ($_FILES["file"]["type"] == "image/pjpeg"))
&& ($_FILES["file"]["size"] < 600000))
  {
  if ($_FILES["file"]["error"] > 0)
    {
    echo "Return Code: " . $_FILES["file"]["error"] . "<br />";
    }
  else
    {
  //  echo "Upload: " . $_FILES["file"]["name"] . "<br />";
   // echo "Type: " . $_FILES["file"]["type"] . "<br />";
   // echo "Size: " . ($_FILES["file"]["size"] / 1024) . " Kb<br />";
  //  echo "Temp file: " . $_FILES["file"]["tmp_name"] . "<br />";

    if (file_exists("upload/" . $_FILES["file"]["name"]))
      {
      echo $_FILES["file"]["name"] . " already exists. ";
      }
    else
      {
      move_uploaded_file($_FILES["file"]["tmp_name"],
      "upload/" . $_FILES["file"]["name"]);
      }
    }
  }
else
  {
  echo "Invalid file";
  }



                                  //this is for inserting data into database


$hostname = "localhost";
$db_user = "**********";
$db_password = "********";
$database = "**********";
//$db_table = "custtable";
$order_table = "order";

$db_table = "hvm_order";

$db = mysql_connect($hostname, $db_user, $db_password);
mysql_select_db($database,$db);
if (isset($_REQUEST['send'])) 
{

$custsql = "INSERT INTO $db_table(name,phone,email,msg,quantity,producttype,status,dor) values ('".mysql_real_escape_string(stripslashes($_REQUEST['name']))."','".mysql_real_escape_string(stripslashes($_REQUEST['phone']))."','".mysql_real_escape_string(stripslashes($_REQUEST['email']))."','".mysql_real_escape_string(stripslashes($_REQUEST['msg']))."','".mysql_real_escape_string(stripslashes($_REQUEST['quantity']))."','".mysql_real_escape_string(stripslashes($_REQUEST['producttype']))."','".mysql_real_escape_string(stripslashes($_REQUEST['status']))."','".mysql_real_escape_string(stripslashes($_REQUEST['dor']))."')";

if($result = mysql_query($custsql ,$db))
 {
echo '<h1>Thank you</h1>Your information has been entered into our database<br><br>';

}
else {
echo "ERROR: ".mysql_error();
}
}
mysql_close();

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Thank you for spending valuable time for me.