Thanks for the info
What I would suggest is please check if you have the same account configured twice in the mail application you are referring.
To see email from different accounts in the Mail app, you need to add them.
On Start, tap or click Mail.
Swipe in from the right edge of the screen, and then tap Settings.
(If you're using a mouse, point to the lower-right corner of the screen, move the mouse pointer up, and then click Settings.)
Tap or click Accounts.
Then check if you have the same account being displayed twice. If that is the case delete once of the accounts and then restart the system and then you should be seeing only single emails.