500内部服务器错误（联系表单，PHP）

Question

We are running a website on a local server. After entering the required data into contact form and clicking the button Send, we get the "500 Internal Server Error". I'm assuming this relates to PHP mail configuration for local servers.

PHP:

<?php
if(isset($_POST["name"]) && isset($_POST["email"]) && isset($_POST["msg"])){
  $name = $_POST["name"];
  $email = $_POST["email"];
  $subject = $_POST["subject"];
  $msg = nl2br($_POST["msg"]);
  $to = "[e-mail]";
  $from = $email;
  $message = "<b>Name:</b> ".$name." <br><b>E-mail:</b> ".$email." <br><b>Subject:</b> ".$subject." <br><p> ".$msg." </p>";
  $headers = "MIME-Version: 1.0" . "
";
  $headers .= "Content-type:text/html;charset=iso-8859-1" . "
";
  $headers .= "From: $from" . "
";
    if(mail($to, $subject, $message, $headers)){
        echo "Success";
    }else{
        echo "The server failed to send the message. Please try again later.";
    }
}
?>

JS:

function _(id){return document.getElementById(id);}
function submitForm(){
  _("submit").disabled = true;
  _("status").innerHTML = "Please wait...";

  var formdata = new FormData();
  formdata.append("name", _("name").value);
  formdata.append("email", _("email").value);
  formdata.append("subject", _("subject").value);
  formdata.append("msg", _("msg").value);

  var ajax = new XMLHttpRequest();
  ajax.open("POST", "contact.php");
  ajax.onreadystatechange = function(){
    if(ajax.readyState == 4 && ajax.status == 200){
      if(ajax.responseText == "Success"){
        _("status").innerHTML = "";
        _("response").innerHTML = "Your message has been successfully sent.";
      }else{
        _("status").innerHTML = ajax.responseText;
        _("submit").disabled = false;
      }
    }
  }
  ajax.send(formdata);
}

Answer 1

Solved. The problem was with the configuration of our local server which runs on MS IIS.