To configure your iPhone for your Office 365 account, go to the settings app, then choose "Accounts", and finally "Add Account".
You will be presented with a list of account choices, choose "Exchange".
In the Exchange screen, fill in the fields with your information:
Email (Your full email firstname.lastname@example.org or email@example.com)
Password (The same password you use for your email and your computer)
Description (a descriptive name for the account such as SUSSMANCORP)
If you get an Unable to Verify Certificate pop-up, tap Accept.
After it verifies your Exchange account information, a new field called "Server" will appear. Enter outlook.office365.com as the server, then tap "Done".
After it your Account information is verified, you will be asked which information you would like to sync. Choose all the options available to sync, then tap "Save" to save your changes.