How Outlook 2007/2010 is shading message headers

There is a feature in Outlook 2007/2010 called "Shade messages headers when reading mail" : it includes next/previous button in front of each replies headers of a message, allowing to go to previous/next replies in the message. I would like to know how Outlook is doing this in order to 开发者_StackOverflow社区reproduce it programmatically.

Thank you

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It just looks for From: at the beginning of a line in the email, nothing more.

You can confirm this by sending yourself an email with the headers out of order:

-----Original Message-----
To: E.J. Dyksen
From: E.J. Dyksen 
Sent: Monday, June 04, 2012 9:35 PM
Subject: RE: Test email

In this case, the line with From: is what Outlook highlights.