Due to security changes, you can no longer use the Android Mail app with a USI account. You should use the Microsoft OUTLOOK App.
To delete your USI account on the Android App
1) Open your email app (red icon). If you are having trouble finding it, swipe upward from your Home Screen, then tap inside the search bar and type "email"
2) Tap on the three vertical dots in the top right (some versions this will be 3 horizontal lines on top left)
3) Tap the Gear/Settings icon.
4) You should see all the accounts set up on this Mail App. Find the USI account and Tap on it.
5) Tap REMOVE in the top right corner - confirm.
***
There may have been some recent changes to the Android mail app- if the above settings do not work try this:
1) Click the red Samsung email app icon
2) Click the "hamburger" icon in top LEFT - looks like 3 horizontal lines
3) Click the Gear/settings icon (top right)
4) Select/click the USI account
5) Click REMOVE (top right).
****
If after removing your USI email account from the Android mail app - you may find that the Contacts in the CONTACTS App disappear - don't despair. Follow the instructions here.