$separator = (uniqid(time()));
$headers .= "Content-Type: multipart/mixed; boundary=$separator" . "n";

$body = "--$separatorn";
$body .= "Content-type: text/html; charset=UTF-8n"; // кодировка письма
$body .= "Content-Transfer-Encoding: 8bitnn";
$body .="Привет. <br>Здесь можно использовать текст в формате <b>HTML</b> <br> "; // и т.д.

for ($j=0;$j<count($files); $j++)
                        {
                        $file=$path_file."soc_price".$files[$j].".zip";
                        $body.= "--$separatorn";
                        $filetype= mime_content_type($file);
                        $body.= "Content-Type: "$filetype"; name==?utf-8?B?".base64_encode("soc_price".$files[$j].".zip")."?=n";
                        $body.= "Content-Transfer-Encoding: base64n";
                        $body.= "Content-Disposition: attachment; filename==?utf-8?B?".base64_encode("soc_price".$files[$j].".zip")."?=nn";
                        $body.= chunk_split(base64_encode(file_get_contents($file)))."n";
                        }
                }

$body.= "--".$separator ."--n";