Re: It's actually used a lot
Outlook Files>property boom look it's the header. Seems easy enough
Notes does it the same way, regardless of client platform (Mac, Windows, Browser)
Outlook? Not so much.
Windows - as you mention, but you have to open/pop-out the message before doing the file..Properties bit (can't do it from inbox directly) and the window is restricted in size. You have to copy and paste into something else to read it in full screen and even at that all you get are the headers, not the whole message source (headers & body/content)
Mac - as in Notes - right click, view source. From inbox without having to open first
Browser - similar to Notes/Mac - right click, View Message Details