Microsoft recently released a new Office Insider build for users in the Monthly Channel (Targeted) level. This Version 1901 (Build 11231.20080) adds @mention support for Word, Excel and PowerPoint, File search in Backstage and more. This build also adds animated gif support in Outlook. Yes, instead of static images, you can now use an animated GIF to make your point. Check out the video demo of this feature below.
— MS Office Insiders (@OfficeInsider) January 23, 2019