A mailbox data storage mechanism for a remote device in a heating, ventilation and air conditioning environment. The mechanism, as a part of a gateway device and acting as a citizen of the heating, ventilation and air conditioning environment, may collect system information regularly and maintain a copy of the latest data locally which can be a response to external access requests in time at any moment. The mechanism may limit the latency for external access and improve user experience. The mechanism may help satisfy multiple interfaces.