While everyone else was raving about the fact that Feedburner can now count RSS subscribers coming from Google reader I've been noticing that there was another discrepancy in the Feedburner data that didn't seem to be accounted for. Below is a screenshot of number of hits from Web browsers on my RSS feed

It seems pretty unlikely that people have clicked on my RSS feed over 5000 times today. At first I thought Feedburner was miscounting feeds that had been subscribed from IE 7 but a quick look in Fiddler shows that IE 7 requests feeds using Windows-RSS-Platform as the User-Agent and is correctly counted by Feedburner.

So I sent some mail to Eric Lunt who's a co-founder and the  CTO of Feedburner to see if he knew what was wrong. He let me know that the problem is that Outlook 2007 doesn't identify itself in the User-Agent string and instead pretends to be Internet Explorer 7. This means there is no way to separate out accesses of your feed from Outlook 2007 from people clicking on your feed in IE 7.

This seems like a fairly rookie mistake to ship in a bigtime product like Outlook. I don't have the latest version installed so I can't confirm that this is truly the case but if it is I hope they plan to fix this soon. It's really lame to not identify your product correctly in the User-Agent string.
Oops. I should have done a search before sending out mail. It looks like this was already covered in a blog post entitled Outlook, RSS, & the user-agent string by Michael Affronti who was the PM for RSS in Outlook 2007. He wrote

For Outlook 2007 we will unfortunately not be able to report any custom user agent string for our RSS aggregation.  Due to the way we integrate with IE across many parts of the application (the WININET stack is the underlying infrastructure for all of Outlook’s internet communication), we cannot easily and safely change the way we broadcast ourselves when connecting to external servers.  To do so would require a fundamental change in the way the WININET stack is called from Outlook and could affect all of the Office applications.  The scope of this fix is unfortunately outside of what we can provide this release.

I guess this won't be fixed anytime soon, if ever. Anyway, I hope this post helps out other users of Feedburner who've also been curious about their weird number of hits supposedly from IE 7.