I'm trying to learn effective DDD practices as I go, but had a fundamental question I wanted to get some clarity on.

I am using ASP.NET WebForms and I am creating a situation where a user places an order. Upon order submission, the code-behind retrieves the user, builds the order from the inputs on the form, calls the User.PlaceOrder() method to perform add the order object to the user's order collection, and calls the repository to save the record to the database. That is fairly simply and straightforward.

Now I need to add logic to send an order confirmation email, and I'm not really sure the proper place to put this code or where to call it. In the olden days I would simply put that code in the code-behind and call it at the same time I was building the order, but I want to get a step closer to solid proper architecture so I wanted to get some information.

Thanks for your help!