We have a Workflow email alert set up to send an email when a customer is confirmed in a training course. The trainers have asked that the email be sent as a calendar invite instead. 

There's a way to automatically generate and attach .ics files using Visualforce email templates. I found that this worked for Outlook, but not for Gmail. Gmail didn't recognize the .ics file so it didn't present a way for me to add the event to my calendar. For some reason, if I create an .ics file by exporting an event (a feature that's only available in Classic) and sending it manually, it works. There's a difference between the .ics file that's generated through a Visualforce email template and one that's created using the export event function, but I'm not sure what it is. 

Has anyone implemented something like this successfully? Any suggestions on how to overcome the above?