Different email depending on payment gateway?

I am offering two different payment options in my online shop: manual (bank transfer) and PayPal.

I would like to send two different "order created" emails, depending on the gateway chosen. I can see there is a place to create some new statuses in the admin area, and I can then make up new emails that link to that status, but how/where do these emails get triggered? I can't find any place where this is defined.