I solve the problem by inserting the following lines at the top of the application's header file (I include it in other files as needed):
#include "resource.h" // main symbols
#include <comdef.h>
#include <pimstore.h>
_COM_SMARTPTR_TYPEDEF(IPOutlookApp, __uuidof(IPOutlookApp));
_COM_SMARTPTR_TYPEDEF(IAppointment, __uuidof(IAppointment));
_COM_SMARTPTR_TYPEDEF(ITask, __uuidof(ITask));
Then, on the application cpp file:
#include "stdafx.h"
#include "MainFrm.h"
#include <initguid.h>
#include "Application.h"
IPOutlookAppPtr g_pPoomApp;
The linker does not complain... Regards, João Paulo Figueira Embedded MVP