When you receive an email notification for a meeting, the meeting is added to your default Calendar and marked New. You can quickly respond to the invitation either from the email Inbox or from the Calendar List pane.
Open the message that contains the meeting request, in either the Inbox or right-click the appointment in the Calendar List.
To respond to the meeting invitation, click Accept, Tentative, or Decline. A reply is automatically sent but you can add comments before you send your response. Before you send your response, you can select the calendar that this meeting should be scheduled on. If you do not select another calendar, your meetings are saved to the default Calendar.
To add comments to a reply when in accepting an invitation from the Calendar View, right-click the invitation and select Edit Reply.
After you make your choice, the email message is moved to the Trash, and New is removed from the calendar meeting notice. Declined appointments display on your calendar in a faded view, as a reminder of the meeting you declined. You can delete declined message any time.
To read the message or to see any attachments that may have been sent, click the meeting notice.
You can move an invitation to another calendar if you do not want it on your default Calendar. Double-click on the meeting notice in the Calendar to open it. The last line in the header is the Calendar field. Select the calendar from the drop-down.