'Following the same design principles as the Office 365 user experience updates announced last year, the ribbon was updated in the new Outlook for Mac to be fully customizable,' explains a Microsoft spokesperson in a statement to The Verge. As you'll see from the screenshot, it's gone.
You can also ignore emails if that's something you need. Part of that means reading and writing emails has been improved, with a whole new email composition interface available. That includes a tweaked design that brings over many of the features that have become maisntays on the web and even in Outlook for iOS and Android. Microsoft is giving Outlook for Mac a fresh coat of paint according to The Verge.