1. Open the Settings app.
2. Navigate to Passwords & Accounts. (May also be listed as Accounts & Passwords)
3. From the Accounts section, select your email address.
4. Tap Delete Account (at the bottom; may require scrolling).
5. To confirm, tap Delete from My iPhone.
6. Tap Add Account, then select Exchange. (It may or may not ask for a selection after clicking Add Account)
7. Enter your email address (and possibly password, but if not, just continue on)
8. It will ask if you want to Sign in with Microsoft, or to configure the settings manually. Choose the Sign In option.
9. It will take you to the Samford login screen, then to the DUO screen. When you approve the DUO notification after sending the Push, you may have to double-tap the home button or swipe up to show your recent apps and you can return to the settings app.
10. Tap Next and wait for it to verify your account.
11. Choose what information from your email account to sync.
12. Tap Save.