calendar invitations - no attendee status update

Hi there,

I have the following setup:

- MacBook Pro mid 2010 running current Mountain Lion

- iCal or BusyCal as Calendar App (this doesn't matter, the issue stays the same)

- Connected Exchange 2010 Account (Mail, Calendar, Contacts), connected Gmail Business Account (Calendar)

The Problem:

When I setup a meeting for my Echange Calendar and just invite people from within my company the attendee status in iCal/BusyCal gets updated based on the attendee's reply. As soon as I invite people for my Exchange Calendar outside my company the attendee status doesn't get updated.

Does anyone have a clue why this happens and even more important does anyone have a clue what to do about it to get this solved.

Thanks,

Manuel