Send attachment with PHP Mail() that should open in outlook - php

Question

I need to send a pdf in email and its receiving fine in gmail, yahoo etc but its giving problem in Microsoft outlook, mail body going as attachment in outlook.Please check below code and tell me what i am missing:--
function sendMailWithAttachment($fromName = 'from name', $fromEmail, $recipient, $mail_body, $subject, $filenamewithpath = '', $cc='',$bcc=''){
$fromEmail = 'info#domain.com';
$filename = explode('/', $filenamewithpath);
$filename = $filename[count($filename) - 1];
$content = file_get_contents($filenamewithpath);
$content = chunk_split(base64_encode($content));
// a random hash will be necessary to send mixed content
$separator = md5(time());
$separator = "==Multipart_Boundary_x{$separator}x";
// carriage return type (RFC)
$eol = "\n";
//$eol = "\r\n";
// main header (multipart mandatory)
$headers = "From: ". $fromName . " <" . $fromEmail . ">\r\n";
if(!empty($cc)){
$headers .= "Cc: <" . $cc . ">\r\n";
}
if(!empty($bcc)){
$headers .= "Bcc: <" . $bcc . ">\r\n";
}
$headers .= "MIME-Version: 1.0" . $eol;
$headers .= "Content-Type: multipart/mixed; boundary=\"" . $separator . "\"" . $eol;
$headers .= "Content-Transfer-Encoding: 7bit" . $eol;
$headers .= "This is a MIME encoded message." . $eol;
// message
$body = "--".$separator.$eol;
$body .= "Content-Transfer-Encoding: 7bit".$eol.$eol;
//$body .= "This is a MIME encoded message.".$eol;
// message
$body .= "--".$separator.$eol;
$body .= "Content-Type: text/html; charset=\"iso-8859-1\"".$eol;
$body .= "Content-Transfer-Encoding: 8bit".$eol.$eol;
$body .= $mail_body.$eol;
/* $body = "--" . $separator . $eol;
$body .= "Content-Type: text/plain; charset=\"iso-8859-1\"" . $eol;
$body .= "Content-Transfer-Encoding: base64" . $eol;
$body .= $mail_body . $eol; */
if($filename != '' && $content != ""){
// attachment
$body .= "--" . $separator . $eol;
$body .= "Content-Type: application/octet-stream; name=\"" . $filename . "\"" . $eol;
$body .= "Content-Transfer-Encoding: base64" . $eol;
$body .= "Content-Disposition: attachment; filename=\"".$filename."\"" . $eol;
$body .= $content . $eol;
$body .= "--" . $separator . "--";
}
//SEND Mail
if(mail($recipient, $subject, $body, $headers)){
return true;
}else{
return false;
}
}