I think you still don't understand. When people star a repository in github they don't expect to get subscribed to a mailing list. If you want to send them emails, ask them explicitly to subscribe to a mailing list.

I think you don't have bad intentions. A "thank you" email looks like a nice detail, but I would consider it borderline spam. I'd probably ignore the first one, but if I ever get a second one I'd hit the "mark as spam" button in gmail.