If your windows mobile or iPhone is stolen or lost, you can send it a command to wipe it's memory clear of any Exchange data:
- Open Outlook Web Access.
 - Log on to the device owner's mailbox.
 - Click Options.
 - In the Navigation pane, select Mobile Devices.
 - Select the ID of the device that you want to wipe and remove from the list.
 - Click Wipe all data from device.
 - Click OK.
 - Click Remove Device from List.