All mobile devices that are enabled for Exchange ActiveSync can use cellular connectivity to synchronize with Exchange 2007. There are several different types of cellular data networks. Regardless of the type of cellular data network that your mobile device uses, the method of synchronization is the same. If the operating system of your device is Windows Mobile 5.0 with the Messaging & Security Feature Pack or Windows Mobile 6.0, synchronization is accomplished through Direct Push. If your device has another operating system, manual synchronization is used. When a device uses Direct Push to synchronize with Exchange 2007, it establishes a long-standing HTTPS connection with the Exchange server. When the connection is first established, the device sets a what is called a heartbeat interval. The default heartbeat interval is 15 minutes. If any new messages are added to monitored folders on the Exchange server within this heartbeat interval, the server informs the device and the device initiates synchronization. When synchronization is complete, a new HTTPS request is initiated and the process is repeated. For more information about Direct Push, see Understanding Direct Push.
Cellular data plans can charge by the minute, by the megabyte, or offer unlimited data transfer. When you use a cellular data connection with Exchange 2007 Direct Push, we recommend purchasing an unlimited data plan.