PHP邮件表单不起作用

我的电子邮件php表单有问题，当我点击提交按钮时，会出现另一个页面，上面写着There was a problem with your e-mail ()我不知道我做错了什么？

这是我的代码：

html代码

<!-- Subscription Form -->
  <form class="email" action="form.php" method="post">
    <input class="get_notified" type="text" placeholder="Enter your email address ..."/>
    <button type="submit" class="go" /></form>
<!-- End Subscription Form -->
    </div>
  </div>
</body>

php代码

<?php
$to = "email@mydomain.com";
$from = "email@mydomain.com";
$headers = "From: " . $from . "'r'n";
$subject = "New subscription";
$body = "New user subscription: " . $_POST['email'];

if( filter_var($_POST['email'], FILTER_VALIDATE_EMAIL) )
{ 
if (mail($to, $subject, $body, $headers, "-f " . $from))
{
    echo 'Your e-mail (' . $_POST['email'] . ') has been added to our mailing list!';
}
else
{
   echo 'There was a problem with your e-mail (' . $_POST['email'] . ')';   
}
}
else
{
echo 'There was a problem with your e-mail (' . $_POST['email'] . ')';   
}