Lee Graber, a biztalk developer in Microsoft, has posted a great post on MessageBox in BizTalk Server. Though he does not blog often, when he does, its a MUST to read. Check hispost from here:
http://blogs.msdn.com/biztalk_core_engine/archive/2007/01/04/what-you-can-and-can-t-do-with-the-messagebox-database-server.aspx
Very interesting stuff!!!