I've blogged about this a bit. See http://blogs.msdn.com/dancre/archive/2004/03/21/93712.aspx for getting started with a .NET plugin, and http://blogs.msdn.com/dancre/archive/2004/04/03/106961.aspx for info on Outlook Redemption, which lets you get around the security prompt issue. There's now a forum on Outlook and .NET at http://www.outlookcode.com/messages.aspx?forumid=5.