Where MAPI fields of mails are stored

I was trying to programatically achieve Communication thread tracking for Outlook. I have found this article on MSDN. And I fiddled with it a bit. It seems that it is possible to do it by trackingPR_CONVERSATION_INDEX by developing Outlook Add In.

However I would like to achieve the similar functionality in Java. Since I am quite new to MAPI development, I was not quite clear about where this PR_CONVERSATION_INDEX is stored in .msg file or somewhere in Exchange server that we access using MAPI.

• I want to know if it is possible to intercept any incoming / outgoing message and obtain itsPR_CONVERSATION_INDEX using Java. If PR_CONVERSATION_INDEX is stored in .msg file then I must be able to parse such file in Java and obtain the same.
• If it is not stored in .msg file then I will like to know where it is stored and how can I access using Java.