Não tenho certeza se esta (pesquisa do google) funciona para você, mas vou citar calbrecht de qualquer maneira:
File > New > Saved Search
Title your search "Unread Mail"
Create the following conditions (located just below the orange search bar): 1. Match if all criteria are met 2. Status | is | Unread 3. Folder | Is Not | Deleted Items (On My Computer)
Save.
Go to the "Mail Views" Section on the left nav column at the bottom. Right click on "Unread Mail" > Add to Favorites Bar.
Now it is easily accessible from the grey favorites bar.