In the 12.0. version we have introduced an ability to invite external Contacts to Pipeliner Appointments.
Follow the steps described below to invite external users and contacts to appointments.
1. Please create an Activity
2. Click the Add button
3. Insert the name of the User or the e-mail address of the Contact you want to invite. Once you add the person, click the + button and invitation will be automatically send to the relevant person.