Email Format php

         $to = $_POST['admin_email'];  // jaha email jayega
         $subject = $_POST['admin_name']." : Contact";  // email subject

  $message = "<h1>".$_POST['admin_name']." : Contact </h1>";
  $message .= "<b>Name : ".$_POST['name']."</b><br/>";
  $message .= "<b>Mobile : ".$_POST['mobile']."</b><br/>";
  $message .= "<b>Email : ".$_POST['email']."</b><br/>";
  $message .= "<b>Message : </b><br/>";
  $message .= "".$_POST['message']."";

 
       
         $header = "From: ".$_POST['admin_email']." \r\n";  // jaha se email jayega
         $header .= "Cc:domin.help24@gmail.com \r\n";   // cc copy email
         $header .= "MIME-Version: 1.0\r\n";
         $header .= "Content-type: text/html\r\n";
       
         $retval = mail ($to,$subject,$message,$header);
       
         if( $retval == true ) {
            $msg =  "Message sent successfully...";
             
         }else {
           $msg =  "Message could not be sent...";
             
         }
 //echo $msg;