php邮件在尝试发送单词“”时中断；localhost”；在电子邮件正文中-太奇怪了

我有一个php邮件表单，买家填写该表单可以向卖家发送电子邮件。一切都很好，只是我正在本地主机MAMP服务器上测试它。

问题：$message1（电子邮件正文）来自$_POST['textarea']。如果有url"http://localhost"通过表单文本区域（放在电子邮件正文中）发送，然后当电子邮件永远不会发送。http://www.anythingelse.com工作良好。。。。我很困惑。是否有一些安全功能可以禁用通过表单发送的本地主机URL？

如果我的代码中还有其他明显的错误，我们将不胜感激。

谨致问候，Daniel

public function saleRequest($seller_email, $seller_username, $buyer_email, $buyer_username, $book_title, $subject1, $message1) {

    define("NAME","xxxxxxx");
    define("FROM",$buyer_email);
    $subject = substr_replace($subject1, '', 30);
    // -=-=-=-=- MAIL HEADERS
    $mime_boundary = md5(time()); 
    $headers = "From: ".NAME." <".FROM.">'n";
    $headers .= "MIME-Version: 1.0'n"; 
    $headers .= "Content-Type: multipart/alternative; boundary='"$mime_boundary'";'n'n"; 
    // -=-=-=-=- TEXT EMAIL PART
    $message = "--$mime_boundary'n";
    $message .= "Content-Type: text/plain; charset=UTF-8'n"; 
    $message .= "Content-Transfer-Encoding: 8bit'n'n"; 
    $message .= wordwrap(stripslashes($message1), 30, PHP_EOL)."'n";
    // -=-=-=-=- HTML EMAIL PART
    $message .= "--$mime_boundary'n"; 
    $message .= "Content-Type: text/html; charset=UTF-8'n"; 
    $message .= "Content-Transfer-Encoding: 8bit'n'n"; 
    $message1 = $message1."this is html";
    $message .= nl2br(wordwrap(stripslashes($message1), 30, "<br>"))."<br>'n";
    // -=-=-=-=- FINAL BOUNDARY
    $message .= "--$mime_boundary--'n'n";
    unset($mime_boundary);
    return mail($seller_email,$subject,$message,$headers);
}