Make sure you have backed up your contacts before doing this!!
After Duo is activated, if your VCSU email on your iPhone native mail app stops working do the following to fix it.
1. Start by tapping on the settings icon on your iPhone.
3. Tap on the account configured for VCSU Email as shown below.
4. Next tap on Delete Account as shown below and confirm the removal.
5. Now go back to the Passwords & Accounts section and tap Add Account.
6. To re-add the VCSU Email account tap on the Exchange icon as shown below.
7. Fill in the necessary information to complete the process.