Deleting Existing Account
Go to Settings on your iPhone and select Mail
Select Accounts
Select your Email
Scroll to bottom and select “Delete Account”
When the window comes up warning you that it will remove calendars, reminders, contacts and notes, select “Delete from My iPhone”.
Add a New Account
Go to Settings on your iPhone and select Mail
Select Add Account
Select Exchange from mail type list
Enter your work email, enter a description (Optional), and select “Next” to go to the next screen.
Enter your password, then select Next.
Select Save the account before navigating away from screen.