Described herein are systems and methods for enabling access to messages on a message service system via user interfaces of receiving client devices. The message service system comprises a message storage system and a message access system. The message storage system receives messages from sending client devices and stores message data. The message access system comprises a message server and UI server. A receiving client device is connected with the UI server through a first HTTP connection for receiving UI data for building webpages of the user interface and is connected with the message server through a second non-HTTP connection for receiving message data for populating the webpages. The UI data does not comprise any message data. A client protocol engine on the receiving client device and a server protocol engine on the message server define and provide the non-HTTP protocol for receiving and transmitting message data.