Invitations not appearing in notificaition sidebar

When I get calendar invitations sent from Outlook, the invitation notification does not show up on the sidebar. Can anyone please help me to fix this so that I do not miss any meetings? It would be really good if em Client automatically added all unread/unconfirmed invitations to my calendar like outlook does, as outlook knows that the email is a calendar invitation no matter what email server I am using.

Hi Sascha, not all calendar invites can be shown in the sidebar, invitations are only shown in the sidebar when the calendar of your sender (and yours as well) support smart scheduling. 

Thank you,

What is smart scheduling? 

That is a feature of your calendar, that other calendars can use to detect your free/busy information and send you an invite to your invitations, without sending you the invitation with the .ics file attached.