public String getStat() {

        int count = 0;
        long allMesagesInBytes = 0;

        for (File box : dir.listFiles()) {
            for (File file : box.listFiles()) {
                if (file.isFile() && file.getName().endsWith(".mail")) {
                    count++;
                    allMesagesInBytes += file.length();
                }
            }
        }
        return "+OK " + count + " " + allMesagesInBytes + CRLF;
    }