User not receiving request for appointments

I have a user who is not being notified of a meeting in his calendar. I sent an invite to a meeting and the meeting was scheduled on his calendar without a response from him accepting, or declining the meeting invite. However, when he sends a meeting requests to me, I am notified and can accept or decline the meeting. I checked his calendar setting and everything appears to be ok. Also had him to run the INbox repair tool. Any other suggestions. We are running Outlook 2003 in a Exchange 2003 environment. Any assistance would be appreciated.