Meeting request sent to person outside of our network show None for the Response after they accept the invitation and send a response

My customer has a SBS 2011 network.  I used Microsoft Exchange 2010 ECM to create a Room Resource.  Example conference room.  To test it I opened my Outlook 2010 and created a Meeting Request.  I invited the Conference Room (conferenceroom@microsoft.com), my account inside the company (andy@microsoft.com) and my account at my office (andy@contoso.com).  I accepted the meeting request and sent a response at my inside and outside email address.  I received all the requests back in my inbox as accepted.  When I go into the meeting request and click Tracking, it show that the Conference Room and my inside account Accepted the meeting.  My outside account still shows the response as None.  

I went into the ECM and changed turned on “Enable the resource booking attendant” in the properties of the Conference Room and tried it again and it still does not work.  I am not sure if I need to turn something else on in the properties of the Room Resource or what.

Thanks
Andy