Hi, I believe you can use the ICS Attachment feature to send out calendar invites in Email Tool. By the way are you involved in the joget project seeing as your username is joget? 

Hi,

It can be done in 2 ways.

(1). Google Calendar Oauth 2.0

Yes you can integrate Google Calendar using bean shell/store binder and send that link in the email. When the user will click Accept in the email, google authentication page will open for access of calendar and once allowed it will be redirected back to the URL you provided in the request and the invitation will be added to their calendar.

(2). Joget Calendar

You can send out emails to all users for the invitation of the event. The content of email will have a customized Accept & Reject Button. On the click of Accept, you call a web service(API) which will update the status of the event for that user. You have a Calendar menu in the userview and you can customize it for each user. There you can show the events which the user will be attending and which he rejected based on your needs.

Here is a link for Calendar Menu.