PHP mail with attachment - Multiple or malformed newlines found in additional_header

Original (now broken code) below:

function mail_attachment($filename, $path, $mailto, $from_mail, $from_name, $replyto, $subject, $message) {

    $file = $path.$filename;
    $file_size = filesize($file);
    $handle = fopen($file, "r");
    $content = fread($handle, $file_size);
    fclose($handle);
    $content = chunk_split(base64_encode($content));
    $uid = md5(uniqid(time()));

    $header = "From: ".$from_name." <".$from_mail.">\r\n";
    $header .= "Reply-To: ".$replyto."\r\n";
    $header .= "MIME-Version: 1.0\r\n";
    $header .= "Content-Type: multipart/mixed; boundary=\"".$uid."\"\r\n\r\n";
    $header .= "This is a multi-part message in MIME format.\r\n";
    $header .= "--".$uid."\r\n";
    $header .= "Content-type:text/plain; charset=iso-8859-1\r\n";
    $header .= "Content-Transfer-Encoding: 7bit\r\n\r\n";
    $header .= $message."\r\n\r\n";
    $header .= "--".$uid."\r\n";
    $header .= "Content-Type: application/octet-stream; name=\"".$filename."\"\r\n";
    $header .= "Content-Transfer-Encoding: base64\r\n";
    $header .= "Content-Disposition: attachment; filename=\"".$filename."\"\r\n\r\n";
    $header .= $content."\r\n\r\n";
    $header .= "--".$uid."--";

    if (mail($mailto, $subject, "", $header)) {
        echo "Mail Sent Successfully to " . $mailto ."<br/>"; // or use booleans here
    } else {
        echo "Mail NOT Sent to " .$mailto ."<br/>";
    }

See the changes made to get this working with our webservers (highlighted in blue):

function mail_attachment($filename, $path, $mailto, $from_mail, $from_name, $replyto, $subject, $message) {
    $file = $path.$filename;
    $file_size = filesize($file);
    $handle = fopen($file, "r");
    $content = fread($handle, $file_size);
    fclose($handle);
    $content = chunk_split(base64_encode($content));
    $uid = md5(uniqid(time()));
    $name = basename($file);
    $header = "From: ".$from_name." <".$from_mail.">\r\n";
    $header .= "Reply-To: ".$replyto."\r\n";
    $header .= "MIME-Version: 1.0\r\n";
    $header .= "Content-Type: multipart/mixed; boundary=\"".$uid."\"\r\n\r\n";
(THIS ENTIRE LINE HAS BEEN CHANGED)
    $nmessage = "--".$uid."\r\n";
    $nmessage .= "Content-type:text/plain; charset=iso-8859-1\r\n";
    $nmessage .= "Content-Transfer-Encoding: 7bit\r\n\r\n";
    $nmessage .= $message."\r\n\r\n";
    $nmessage .= "--".$uid."\r\n";
    $nmessage .= "Content-Type: application/octet-stream; name=\"".$filename."\"\r\n";
    $nmessage .= "Content-Transfer-Encoding: base64\r\n";
    $nmessage .= "Content-Disposition: attachment; filename=\"".$filename."\"\r\n\r\n";
    $nmessage .= $content."\r\n\r\n";
    $nmessage .= "--".$uid."--";
error_reporting(E_ALL);
    if (mail($mailto, $subject, $nmessage, $header)) {
        echo "Mail Sent Successfully to " . $mailto ."<br/>"; // or use booleans here
    } else {
        echo "Mail NOT Sent to " .$mailto ."<br/>";
    }

}

I hope this helps someone . Thanks to mindofdes to share the code. :)