Android 2.2 has come up with a new feature called "Remote Wipe" which wipes out the data in the Android phone remotely in case the device is lost. For this we were using Microsoft Exchange Server to wipe data in phone remotely. But for this to possible tha phone should in the network coverage area? If the phone is not there in Network Coverage area , how can the data can be wiped from remote Microsoft Exchange Server?
Your server has to be able to communicate with the phone somehow to send the wipe message, either by a phone network connection, or if it's connected to one of its saved Wifi connections. Not 100% sure about the Android implementation, but normally the message will queue up and be received when the phone comes into coverage. The phone also has to be switched on at some point, or it'll never be received.
This is a limitation of all phones that have remote wipe capability (eg Windows Phone, Blackberry, etc). It can't send the signal by magic!