我无法使用mail() PHP函数发送消息

我无法在代码中找到错误。我的PHP代码在我的index.html文件中。我无法从我的静态网页发送消息。

<div class="col-md-6">
    <form action="index.html" method="POST" class="contact-form" role="form">
        <input type="text" class="form-control" id="fname" name="fname" placeholder="Your Full Name">
        <input type="email" class="form-control" id="email" name="email" placeholder="Your E-mail">
        <input type="text" class="form-control" id="subj" name="subj" placeholder="Your Subject">
        <textarea id="mssg" name="mssg" placeholder="Your Message" class="form-control" rows="10"></textarea>
        <input class="btn btn-main btn-lg" type="submit" id="submit" name="submit" data-loading-text="<i class='fa fa-spinner fa-spin'></i> Sending...">
    </form>
</div>

<?php
if (isset($_POST['submit'])) {
    $to = 'email@company.com';
    $siteName = 'http://www.website.com';
    $name = $_POST['fname'];
    $mail = $_POST['email'];
    $subject = $_POST['subj'];
    $message = $_POST['mssg'];
    $mailSub = '[Contact] [' . $siteName . '] '.$subject;
    $body = 'Sender Name: ' . $name . "'n'n";
    $body .= 'Sender Mail: ' . $mail . "'n'n";
    $body .= 'Message Subject: ' . $subject . "'n'n";
    $body .= 'Message: ' . $message;
    $header = 'From: ' . $mail . "'r'n";
    $header .= 'To:  ' . $to . "'r'n";
    mail($to, $mailSub, $body, $header);
}else{
    echo '0';
}
?>

我收到一个错误，每次我试图通过我的网站发送消息。谢谢你！