Haven't tried this. Make sure the shortcut you use to open Outlook does
NOT have the /recycle parameter (which force reuse of an existing
running instance of outlook.exe). Using the Mail applet in Control
Panel, make sure you actually do have more than mail profile. Then
configure to prompt for a profile (when Outlook gets loaded). Maybe you
then get to select a different profile for each instance of Outlook that
is loaded.
Seems a waste, however. Why do you need multiple mail profiles open
concurrently? I suspect you want to do something that is already
available but you are taking the wrong route to the solution.