I am not sure if this was posted earlier, but Outlook 2000 Rich Text messages seem to contain full path to user's mail box. Admittedly this is not much, but since by default Outlook creates it's mailbox in the profile directory, I might get the username and possibly OS version (C:\WINNT\Profiles\johns\<blahblah>\mailbox.pst for example )
This archive was generated by hypermail 2b30 : Thu Aug 02 2001 - 12:44:33 PDT