PHP 表单大约 30% 的时间不通过电子邮件发送信息

我收到"此消息没有内容"错误，大约 30% 的时间访问者填写表单并且无法隔离问题。用于发送电子邮件的 php 如下，地址是匿名的。有什么想法吗？

到目前为止，我试图在论坛中找到答案，但无济于事。感谢您的帮助！

<?php
    $fromAddress = 'x@www.com';
    $subject = 'Resources - White Paper Download - '.$_POST['WhitePaper'];
    $message .= "'r'n";
    foreach($_POST as $name => $value) {
    $message .= $name . ': ' . $value . "'r'n";
    }
    $to       = 'y@www.com';
    $headers  = 'MIME-Version: 1.0' . "'r'n";
    $headers .= 'Content-type: text/plain; charset=UTF-8' . "'r'n";
    $headers .= 'From: ' . $fromAddress . "'r'n" .
        'Reply-To: ' . $fromAddress . "'r'n" .
        'X-Mailer: PHP/' . phpversion(). "'r'n";
    $headers .= 'Cc: z@www.com, <t@www.com>' . "'r'n";
    mail($to, $subject, $message, $headers);
    echo "mail sent";
?>