The Unread Mail folder is a default Outlook Search Folder. If it isn't visible in your Folders list, you can add it.
In Mail, click the Folder tab.
In the New group, click New Search Folder.
Tip
You can also open the New Search Folder dialog box by pressing CTRL+SHIFT+P.
In the Reading Mail section, click Unread mail.
Click OK.
Note
Use these same steps to add any default Search Folder. In step 2, in the New Search Folder dialog box, click the Search Folder that you want to add.