E-Mail Invoice auto created by Subscription to customer

I finally managed to create a subscription plan and a subscription. The invoice got created automatically. YAY… (perhaps I should have tried the Auto-Repeat feature first… but now the subscription ist working).

But I need help with this last step: The customer does not know about the new invoice, because it got not mailed automatically.

I tried to set up a new Notification for this, but I only want to fire this, if the invoice is auto generated by a subscription - how can I do this?

did you find a solution to auto send the invoice?

How do you do this?
I create Subscription by code when customer sign up to my site.
But after free Trialling period, the status is not changed to Active and no invoice is created.
Thank you