public String setRSET() {

        int count = 0;
        File rsetFile;
        String rsetFileName;

        for (File box : dir.listFiles()) {
            for (File file : box.listFiles()) {
                if (file.isFile() && file.getName().endsWith(".mail")) {
                    count++;
                    rsetFileName = file.getName();
                    if (rsetFileName.startsWith("TODEL")) {
                        rsetFileName = rsetFileName.trim().split(" ")[1];
                        rsetFile = getFile(rsetFileName);
                        file.renameTo(rsetFile);
                    }
                }
            }
        }
        return "+OK maildrop have " + count + " message" + CRLF;
    }