Outlook 2016 for Mac is being updated for Office Insiders on the Fast Ring.
These Insider builds for Office 2016 for Mac provide new or improved features, security updates and bug fixes.
August 23, 2017 release changelog
Version: 15.38 (170822)
New or improved features:
Mail Headers: Improved look and functionality for mail and meeting invitation headers (in Reading Pane and separate window) – Details
Week Numbers: In Calendar view, week numbers are now displayed in Month view (Grid view) and in the mini-calendar in the Sidebar. If you click on the week number in the mini-calendar, your calendar will change to display that week
When composing a message, duplicate Attach File buttons are no longer displayed in the Ribbon
When using spacebar key to press view selection buttons in the Sidebar, keyboard focus now remains on the button pressed
macOS High Sierra: If you have the Cisco WebEx plugin installed, Outlook might crash – Details
When composing a message, dragging and dropping contacts between To, Cc, and Bcc fields requires selecting, clicking, and holding before dragging
To download the latest update, Open the Outlook app and go to Help >> Check for Updates (top menu).