Cannot get field from $_POST array when form has enctype="text/plain"

I believe that my code is correct, when I remove the isset statement it returns an error as if the fields were not set. I have heard that this may be due to how PHP is configured on the server which may be the case. It seems like the variables aren't being passed from the HTML to the PHP code. If it means anything I have my PHP installed with WebPlatformInstaller and running IIS on windows server 2016

<?php
echo "test";

    if(isset($_POST['email'])) {
        echo "success";
        $email_to = "temp@gmail.com";
        $email_subject = "Your email subject line";

        function died($error) {
            // your error code can go here
            echo "We are very sorry, but there were error(s) found with the form you submitted. ";
            echo "These errors appear below.<br /><br />";
            echo $error."<br /><br />";
            echo "Please go back and fix these errors.<br /><br />";
            die();
        }


        // validation expected data exists
        if(!isset($_POST['email']) ||
            !isset($_POST['message'])) {
            died('You must enter your email and a message');       
        }


        $email_from = $_POST['email']; // required
        $message = $_POST['message']; // required

        $error_message = "";
        $email_exp = '/^[A-Za-z0-9._%-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,4}$/';

        if(!preg_match($email_exp,$email_from)) {
        $error_message .= 'The Email Address you entered does not appear to be valid.<br />';
        }

        $string_exp = "/^[A-Za-z .'-]+$/";

        if(strlen($message) < 2) {
        $error_message .= 'The message you entered do not appear to be valid.<br />';
        }

        if(strlen($error_message) > 0) {
        died($error_message);
        }

        $email_message = "Form details below.\n\n";


        function clean_string($string) {
          $bad = array("content-type","bcc:","to:","cc:","href");
          return str_replace($bad,"",$string);
        }

        $email_message .= "Email: ".clean_string($email_from)."\n";
        $email_message .= "message: ".clean_string($message)."\n";

        // create email headers
        $headers = 'From: '.$email_from."\r\n".
        'Reply-To: '.$email_from."\r\n" .
        'X-Mailer: PHP/' . phpversion();
        @mail($email_to, $email_subject, $email_message, $headers);  
        ?>

        <!-- include your own success html here -->

        echo "Thank you for reaching out! I'll be in touch.";

        <?php

        }
        ?>`

HTML

<form action="contact.php" method="post" enctype="text/plain">
      <input type="email" placeholder="Email" name='email' required>
      <input class="btn" type='submit' tabindex="1" value='Send'>
      <textarea type='text' name='message' required></textarea>
    </form>

Read this: Bug #33741 $_POST superglobal not populated which is about Your issue.

and answer there:

Valid values for enctype in tag are:

application/x-www-form-urlencoded

multipart/form-data

Check these screenshots with code samples to see results:

text/plain

application/x-www-form-urlencoded

EXTRA: php://input stream

as request body it does not change anything but @ symbol (that's why it's urlencoded)

RESULT: It's not a bug of PHP, it's common feature for all PHP versions to accept supported enctypes, it just does not populate $_POST array from php://input when it "see" different content-type. But if You insist You can read it from php://input stream.

link to manual