and Google Apps. While individual users may be able to use a wireless provider's email services without having to install BES themselves, organizations with multiple users usually run BES on their own network. BlackBerry devices running BlackBerry OS 10 or later can also be managed directly by a Microsoft Exchange Server, using Exchange ActiveSync (EAS) policies, in the same way that an iOS or Android device can. (EAS supports fewer management controls than BES does.) Some third-party companies provide hosted BES solutions. Every BlackBerry has a unique ID called a BlackBerry PIN, which is used to identify the device to the BES. BlackBerry at one time provided a free BES software called BES Express (BESX). The primary BES feature is to relay email from a corporate mailbox to a BlackBerry phone. The BES monitors the user's mailbox, relaying new messages to the phone via BlackBerry's Network Operations Center (NOC) and user's wireless provider. This feature is known as push email, because all new emails, contacts, task entries, memopad entries, and calendar entries are pushed out to the BlackBerry device immediately (as opposed to the user synchronising the data manually or having the device poll the server at intervals). BlackBerry also supports polling email, through third-party applications. The messaging system built into the BlackBerry only understands how to receive messages from a BES or the BIS, these services handle the connections to the user's mail providers. Device storage also enables the mobile user to access all data off-line in areas without wireless service. When the user reconnects to wireless service, the BES sends the latest data. A feature of the newer models of the BlackBerry is their ability to quickly track the user's current location through trilateration without the use of GPS, thus saving battery life and time. Trilateration can be used as a quick, less battery intensive way to provide location-aware applications with the co-ordinates of the user. However, the accuracy of BlackBerry trilateration is less than that of GPS due to a number of factors, including cell tower blockage by large buildings, mountains, or distance. BES also provides phones with TCP/IP connectivity accessed through a component called MDS (Mobile Data System) Connection Service. This allows custom application development using data streams on BlackBerry devices based on the Sun Microsystems Java ME platform. In addition, BES provides network security, in the form of Triple DES or, more recently, AES encryption