For the Inbox you need:
oFolder = oNameSpace.GetDefaultFolder(6)

Iterate through the GetDefaultFolder from 3 to 16 to reference all Outlook folders.

>oOutlook = CREATEOBJECT("Outlook.Application")
>oNameSpace = oOutlook.GetNameSpace("MAPI")
>oFolder = oNameSpace.Folders(1)
>
>For some reason, this does not work:
>oFolder = oNameSpace.Folders("Inbox")
>