Microsoft Exchange provides email, contact, tasks, and calendar information that you can automatically sync wirelessly to iPhone. You can set up an Exchange account directly on iPhone.
Set up an Exchange account on iPhone: Go to Settings > Mail, Contacts, Calendars. Tap Add Account, and then tap Microsoft Exchange.
Ask your service provider or administrator what settings you should use.
This article will work on all iPhones using iOS 6; including iPhone 3GS, iPhone 4, iPhone 4S, and iPhone 5.