You can schedule automatic synchronization between your device and Microsoft Exchange every time an item arrives or is changed in Microsoft Exchange, after your first full synchronization with Microsoft Exchange. You can synchronize information automatically as items arrive only if your company is running Microsoft Exchange with Exchange ActiveSync.
Note
To set the days and hours that make up your peak and off-peak times, click Change Times.
Some devices or versions of Microsoft Exchange may also require you to specify a device address to use this feature.
See also
Change the synchronization schedule
Synchronize with Microsoft Exchange