php mail() issues?

See attached.

This function has been used since Dec. 31, 2014 (date last changed) until last Friday. It has been executed hundreds of times successfully.

Starting then, it produces the error message "mail send ... ERROR!"

In the attached version, I added the php error reporting at the top,

It now shows:

Warning: mail(): Multiple or malformed newlines found in additional_header in /home/fwsprinkler/public_html/fwsprinklercdb.info/mail_attachment.php on line 28
kk =
mail send ... ERROR!

Is it possible that the host upgraded the version of php & the newer version has some issue with this?

<?php
function mail_attachment($filename, $path, $mailto, $from_mail, $from_name, $replyto, $subject, $message) {
	error_reporting(E_ALL);
	ini_set('display_errors', 1);
    $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";
    $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"; // use different content types here
    $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."--";
	$kk = mail($mailto, $subject, "", $header);
	echo "kk = " . $kk . "<br>";
    if ($kk) {
        echo "mail send ... OK"; // or use booleans here
    } else {
        echo "mail send ... ERROR!";
    }
}
?>

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mail-attachment.php