Exchane Email Archiving

We are looking for an archiving solution for MS Echange servers that is a little different from the normal.

I have seen several archiving solutions that capture email messages as they are passing through the server and maintaining a copy in the archive. These are all good solutions but they don't maintain the folder structure under the Inbox.

What we are looking for is a solution that scans the Inboxes periodically and harvests the email messages located there maintaining the folder structure as the user built it in Outlook. Has anyone seen such a system available?