AddEventHandler('main', 'OnBeforeEventAdd', 'includeCustomMail');

function custom_mail($to, $subject, $message, $additional_headers, $additional_parameters) {
try {
    $messagePostfix = '';
    $un = strtoupper(uniqid(time()));
    $eol = CAllEvent::GetMailEOL();

    // Ищем инструкции по подключеннию файлов и выполняем их
    // ADD-FILE: #CARD1#=>card1.jpg;#CARD2#=>card2.jpg;
    $additional_headers = preg_replace_callback('#^s*ADD-FILE:s*([^rn]+)(?:[rn]+|$)#sim', function ($m) use (&$messagePostfix, $un, $eol) {
        $strAddFile = trim(mb_decode_mimeheader($m[0]));
        if (empty($strAddFile)) {
            return '';
        }
        // Разбираемся какие файлы подключать
        // #CARD1#=>card1.jpg;#CARD2#=>card2.jpg;
        $arrFileAa = preg_split('#s*;s*#', $strAddFile, -1, PREG_SPLIT_NO_EMPTY);
        foreach ($arrFileAa as $strFileAs) {
            // #CARD1#=>card2.jpg
            $arrFileAs = preg_split('#s*=>s*#', $strFileAs, -1, PREG_SPLIT_NO_EMPTY);
            // Открываем файл
            $f = fopen($arrFileAs[0], 'rb');
            if ($f === false) {
                $fileData = 'Сan not open file ' . $arrFileAs[0];
                $fileName = $arrFileAs[1] . '.txt';
            } else {
                $fileData = fread($f, filesize($arrFileAs[0]));
                $fileName = $arrFileAs[1];
                fclose($f);
            }
            $messagePostfix .= '--------' . $un . $eol;
            $messagePostfix .= 'Content-Type: application/octet-stream;name="' . $fileName . '"' . $eol;
            $messagePostfix .= 'Content-Disposition:attachment;filename="' . $fileName . '"' . $eol;
            $messagePostfix .= 'Content-Transfer-Encoding: base64' . $eol . $eol;
            $messagePostfix .= chunk_split(base64_encode($fileData)) . $eol . $eol;
        }
        return '';
    }, $additional_headers);

    // Нужно ли добавлять файлы
    if ($messagePostfix) {
        $messagePrefix = '--------' . $un . $eol;
        $additional_headers = preg_replace_callback('#^s*(Content-Type:[^rn]+)(?:[rn]+|$)#sim', function ($m) use (&$messagePrefix, $eol) {
            $messagePrefix .= $m[1] . $eol;
            return '';
        }, $additional_headers);
        $additional_headers = preg_replace_callback('#^s*(Content-Transfer-Encoding:[^rn]+)(?:[rn]+|$)#sim', function ($m) use (&$messagePrefix, $eol) {
            $messagePrefix .= $m[1] . $eol;
            return '';
        }, $additional_headers);
        $additional_headers = trim($additional_headers) . $eol;
        $additional_headers .= 'Mime-Version: 1.0' . $eol;
        $additional_headers .= 'Content-Type:multipart/mixed;boundary="------' . $un . '"' . $eol . $eol;

        $message = $messagePrefix . $eol . $eol . $message . $eol . $eol . $messagePostfix;
    }

    // file_put_contents($_SERVER['DOCUMENT_ROOT'] . DIRECTORY_SEPARATOR . 'mail.txt', $additional_headers . $message);

    if ($additional_parameters != '') {
        return @mail($to, $subject, $message, $additional_headers, $additional_parameters);
    }
    return @mail($to, $subject, $message, $additional_headers);
} catch (Exception $e) {
    return false;
}