Some flows define a Due date. It became a user case on our project to provide ability to send on demand or system notification emails as calendar invite. In our case it is Outlook mail engine. option for on demand: when a date control is used with assigned person, a transition to enable a calendar invite to be sent to the assigned person with the due date and potentially addition of a link to the form or inclusion of user selcted bindings; Option for automated invite: once form is submitted and there are "Assigned to" and "Due date" the system notification is issued as calendar event rather than plain email.