This article goes over the procedure for updating or entering your password into Mail app in iOS. This can happen either when your password has changed or when two factor authentication has expired.
1. You will see a prompt to Enter the password for Exchange account with your email listed. Tap Edit Settings.
2. If you get the prompt to Enter the password again, always tap Cancel until this process is complete.
3. On the Settings > Passwords & Accounts page, tap on your Exchange account under Accounts section. (It's labeled "UWGB" in the picture, but can be named "Exchange" or anything else you may have changed it to.)
4. Tap Re-enter Password.
5. You may be prompted whether to sign in with "Work or school account" or a "personal account." Tap "Work or school account."
6. It should then take you to UWGB's Single Sign-On page. Enter your campus password.
7. You will then be prompted for two factor authentication. Tap Send Me a Push.
8. You will get a two factor authentication notification on your configured device. Accept the login.
9. If you use two factor authentication app on the same device you are configuring the Mail app, it will have switched to the two factor authentication app instead of the Settings app. You will need to switch back to the Settings app. You can either go home and click on Settings app again, or swipe through the open apps on your device.
10. A screen will ask: "Are you trying to sign in to Apple Internet Accounts?" Tap Continue.