Scott Hanselman discovered that Outlook is using proprietray feed URI schemes under-the-hood; OUTLOOKFEED: and OUTLOOKFEEDS:. As if the feed: URI scheme wasn't already dumb enough, now Microsoft is going and breaking the architecture of the web again. Let's just hope that this is an internal thing that'll never find its way onto the WWW.
http://www.hanselman.com/blog/Outlook2007BetaIntroducesItsOwnFeedURLProtocolEw.aspx
Thanks to Marjolein Hoekstra for the link.
Update: Microsoft officially removed the OUTLOOKFEED: and OUTLOOKFEEDS: URI schemes along with the broader "Feed" functionality in 2024 as part of retiring the Feed feature across Microsoft 365, Outlook Mobile, Edge’s Work Feed, and related apps. After that date, those custom protocols are no longer supported.
