When you receive an email notification for a meeting, the meeting is added to your 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 the appropriate action. If the meeting is a recurring meeting, you have the option to select Instance or Series to respond to.
Click Accept,
Tentative, or Decline.
Zimbra automatically sends a reply. You can add comments before you send
your response.
To add comments when in Calendar View, right-click and select Edit Reply.
After you make your choice, the email message is moved to the Trash, and New is removed from the calendar 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.