Providing sync notifications to client devices

Providing synchronization notifications to a client device. In response to a server receiving notification that an event of interest has been received, a state of the client device is determined. The state indicates whether or not the client device has any outstanding sync notifications. In an embodiment, the state is determined based on a first parameter and a second parameter. When the state of the client device indicates that the client device has no outstanding sync notifications prior to the receipt the received notification, the first parameter is set equal to the second parameter, and the second parameter is updated after each successful device synchronization of the client device. A filter is applied prior to sending out the sync notification to the client device.