@Override
    public boolean equals(Object obj) {
        if (!super.equals(obj)) {
            return false;
        }

        MailSubscription o = (MailSubscription) obj;
        return (address == null ? o.address == null : address.equals(o.address)) &&
               (city == null ? o.city == null : city.equals(o.city)) &&
               (country == null ? o.country == null : country.equals(o.country));
    }