Assuming you are attempting to use Outlook via the PB mail objects, a default Outlook mail profile needs to exist on the machine running the PB app, at least this is how Outlook works when using OLE objects instead of the MAPI objects from a PB app. If the mailLogon method is unable to locate an Outlook profile, it will fail.
Since multiple users will be running the app from one machine/server, you may need to create an Outlook mail profile on that machine for each user.
I'm not an Outlook Admin, so I suggest you confer with your Outlook Administrator if you have one, or search MSDN for information on Outlook mail profiles.
HTH