mPDF funguje na google, ne na Seznamu

<?php 

include("mpdf/mpdf.php");

$html = '....';

$mpdf=new mPDF('utf-8', 'A4', '0', '10', '10', '10', '10', '10');
$mpdf->WriteHTML($html);

$content = $mpdf->Output('', 'S');

$content = chunk_split(base64_encode($content));
$mailto = '...@seznam.cz';
$from_name = 'Text s diakritikou';
$from_mail = '...@....cz';
$replyto = '...@....cz';
$uid = md5(uniqid(time()));
$subject = 'Objednávka č. ';
$message = 'Automaticky vygenerovaná faktura...';
$filename = 'xxx.pdf';

$header = "From: ".$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='UTF-8'\r\n";
$header .= "Content-Transfer-Encoding: 7bit\r\n\r\n";
$header .= $message."\r\n\r\n";
$header .= "--".$uid."\r\n";
$header .= "Content-Type: application/pdf; name=\"".$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."--";
mail($mailto, $subject, "", $header);

exit;
?>