Add Your CIIS Email to the iPhone Mail App 

Go to your Settings, select "Mail"

Choose "Accounts"

Select "Add Accounts

Choose Microsoft Exchange

Input your CIIS email and click "Next"

Choose "Sign In"

Input your password to your CIIS email.

Approve sign-in request through Microsoft Authenticator. Remember the number that is shown in the sign-in request. Enter the number into the Microsoft Authenticator App and click "Yes"