How to send order confirmation via Hook

Hi,

I have a custom hook which sets the order status regrading to the payment method. This custom hook is needed in my case. I want to send from this hook the -in other cases- automatic “payment successful” email. How can I do this? Have you a bit of code? The paypal integration of woocommerce uses this mail but I have not found the part of code where this mail is triggered.

Thanks!