When you are using the appointment confirmation e-mail function of Plan-IT, since version 5.171.7825 (january 2017) it is possible to send a agenda item along.
How to turn this on
In the menubar, click on the option System.
Select the option System settings.
In the first row of tabs, go to Connections.
Then to go Mail in the second row of tabs.
Turn on the option Send agenda item with appointment confirmation.
The last step is to go to the Plan-IT folder and create (or let your system administrator create it) an extra folder with the name Export. Sending the agenda item does not work when the Export folder does not exist.
After the above settings have been configured, a agenda item is automatically sent with every appointment confirmation e-mail.