It looks like the Mail app on the Windows 10 Insider Fast Ring is getting image previews according to a tip from one of our readers. Straight from the message list, Leo Varela was able to view picture attachments as a preview of the contents.
The early availability of the message list image previews seems to only be working for some Fast ring devices, while others don't. Similarly, some users can see the option as a grayed out feature 'not available for any of their accounts'.
It's curious to see the feature pop up without pomp and circumstance. Do you have the image preview feature on your Mail app? We'd love to hear your reports!
Thanks to Leo Varela for the tip!