The iPhone and iPad use Microsoft Exchange ActiveSync, to push your Mail, Contacts, and Calendar data to your iPhone.
*Note - Setting up these instructions will override any Contacts or Calendars already on the device. Please back those up prior to following these steps as they are not recoverable.
1. Setup your Exchange e-mail account by selecting the Settings icon.
2. Select Passwords & Accounts.
3. Select Add Account
4. Select Microsoft Exchange
5. Use the following settings and then select Next.
Email: firstname.lastname@example.org (the user's full email address)
Domain: (leave blank)
User Name: email@example.com (the user's full email address)
Password: (the user's password)
6. Select what you would like to sync to the iPhone and then press Done.