PHP mail function doesn't complete sending of e-mail

<?php $name = $_POST['name']; $email = $_POST['email']; $message = $_POST['message']; $from = 'From: yoursite.com'; $to = 'contact@yoursite.com'; $subject = 'Customer Inquiry'; $body = "From: $name\n E-Mail: $email\n Message:\n $message"; if ($_POST['submit']) { if (mail ($to, $subject, $body, $from)) { echo '<p>Your message has been sent!</p>'; } else { echo '<p>Something went wrong, go back and try again!</p>'; } } ?> I've tried creating a simple mail form. The form itself is on my `index.html` page, but it submits to a separate "thank you for your submission" page, `thankyou.php`, where the above PHP code is embedded. The code submits perfectly, but never sends an email. How can I fix this?