To delete:

• From the Home screen, tap Settings > Mail > Account

• Under Accounts, tap on the email account you want to delete.

• Tap Delete Account > Delete from My iPhone.

To Add:

• Go to Settings > Mail, then tap Accounts.
• Tap Add Account, then select Exchange

• Enter your email address and an optional description for the account. Click Sign In; then a prompt will pop up asking if this is a Work/School account or a personal account, select Work/School.

• At this point the FAU SSO window will appear for you to enter your Username/ password and approve Duo when prompted.

• Tap Next and wait for Mail to verify your account. 
• Choose information from your email account, like Contacts or Calendars.
• Tap Save.