IE had "native RSS" going back to somewhere around IE4 or IE5. There was some "Active Desktop" nonsense you could do with RSS really early on, which would have been IE4. IE's approach was very similar to Firefox's: clicking an RSS feed would give you a pretty printed XML page by default, which wasn't exactly useful, but might also have side links to some use cases for RSS depending on some combinations of addons installed and configured preferences.
Just like Firefox at the time, the most common built-in usecase was that you could subscribe an RSS feed as an auto-updating Bookmarks Folder. But there were addons that did all sorts of things and some feed readers supported various sorts of integrations with IE.
IE even shared its feed reading engine as a shared COM control with a built-in Windows service. It was something like BITS [Background Intelligent Transfer Service], Windows' background downloader service, where you could hand it feeds, it would manage feed polling, it tried to be smart about it with things like exponential back-off and downloading feeds during idle bandwidth periods on your machine, and give you back a very simple RSS-like data store of whatever it found. Outside of IE using it, so far as I know the only other major "feed reader" to integrate it was Outlook. I think even fewer people (I did) made use of the RSS features in Outlook than made use of the RSS features in IE and almost no one made use of the fact that IE and Outlook had a shared view of the same feeds, but when IE dropped native RSS is when Outlook dropped RSS support because they didn't want to own the feed reading engine.
Just like Firefox at the time, the most common built-in usecase was that you could subscribe an RSS feed as an auto-updating Bookmarks Folder. But there were addons that did all sorts of things and some feed readers supported various sorts of integrations with IE.
IE even shared its feed reading engine as a shared COM control with a built-in Windows service. It was something like BITS [Background Intelligent Transfer Service], Windows' background downloader service, where you could hand it feeds, it would manage feed polling, it tried to be smart about it with things like exponential back-off and downloading feeds during idle bandwidth periods on your machine, and give you back a very simple RSS-like data store of whatever it found. Outside of IE using it, so far as I know the only other major "feed reader" to integrate it was Outlook. I think even fewer people (I did) made use of the RSS features in Outlook than made use of the RSS features in IE and almost no one made use of the fact that IE and Outlook had a shared view of the same feeds, but when IE dropped native RSS is when Outlook dropped RSS support because they didn't want to own the feed reading engine.