PHP send mail

[sabodden]

I want to make a donate form for my server, i follow a tutorial step by step to do it in php, but don't work
It is not showing any error, it's redirecting but not sending the e-mail...

Why?

code:
confirm.php

<form action="mail_donate.php" method="post">
  <label for="email">Your e-mail:</label><br>
  <input type="text" id="email" name="email"><br>
  
  <label for="character">Your character name:</label><br>
  <input type="text" id="character" name="character"><br>
  
  <label for="code">Certificate code:</label><br>
  <input type="text" id="code" name="code"><br>

  <label for="note">Note you want to send:</label><br>
  <input type="text" id="note" name="note"><br><br>

  <input type="submit" value="Submit">
</form>

mail_donate.php

<?php 
    if(isset($_POST['submit'])){
        $to = "[email protected]"; // this is your Email address
        $from = $_POST['email']; // this is the sender's Email address
        $subject = "donate [". $_POST['character'] . "]";
        $message = "Email: ". $_POST['email'] . "\nCharacter: " . $from . "\nCode: " . $_POST['code'] . "\nNote: " . $_POST['note'];

        $headers = "From:" . $from;
        mail($to,$subject,$message,$headers);
    }
    $host = $_SERVER['HTTP_HOST'];
    $extra = 'thank_you.php';
    header("Location: $extra");
?>