Some outlook users want to see only the flagged or unread messages in their Outlook mail list in order to easily deal with them on time. 

In this video you will learn how to view only unread or flagged emails in Outlook. 

Click on the filter email, select unread. 
You will see all unread emails. 
Then again click on the filter email select flagged. 
Now you will see your all flagged emails.