Microsoft is rolling out a big update for Outlook on Windows and web with design improvements. Microsoft has added a new option called Coming Soon in Outlook for Windows and an opt-in toggle in Outlook on the web that allows users to try the new design. The update will begin rolling out to customers in the Monthly Channel (Targeted) and Targeted Release program in the next few weeks. Microsoft says the update will make reading, composing, and taking action in emails and meetings faster.
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-is-updating-outlook-on-windows-and-web-with-design-improvements/