我想在新用户注册时收到新注册的邮件，但它无法正常工作

Question

没有邮件功能插入查询工作正常，但使用邮件功能，该页面将无法正常工作页面无法处理此请求。提供HTTP ERROR 500，它会在每次新注册时向我们发送电子邮件。

<?php
require_once 'sessions.php';;

$servername = "localhost";
$username = "medmocksroot";
$password = "medmocks123";
$dbname = "medmocks";

// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}

$sql = "INSERT INTO student (Name,Contact,email,Password)
VALUES ('$_POST[name]','$_POST[contact]','$_POST[email]','$_POST[password]')";

if ($conn->query($sql) === TRUE) {
    $_SESSION['message'] = "Request Submitted Successfully";
} else {
    $_SESSION['message'] = "Error: " . $sql . "<br>" . $conn->error;
}
/*header("Location: signup.php");*/

if (isset($_REQUEST['signup_mail']))  {

  //Email information
  $admin_email = "medmocks7@gmail.com";
  $name = $_REQUEST['name'];
  $subject = "New Signup";
  $email = $_REQUEST['email'];
  $contact = $_REQUEST['contact'];
  $pass = $_REQUEST['password'];


  //send email

$sql = mail("medmocks7@gmail.com",  "Subject:" .$subject, "From:" .$email, "Name:" .$name, "Contact:" .$contact, "Password:" .$pass);

if ($conn->query($sql) === TRUE) {

  header("Location:signup.php");

  echo '<script language="javascript">';
  echo 'alert("Message Sent Successfully")';  //not showing an alert box.
  echo '</script>';
  exit;

} else {
    echo "Error: " . $sql . "<br>" . $conn->error;
}

$conn->close();