This is a simple one. Download the module https://appstore.home.mendix.com/link/app/259/Mendix/E-mail-module-with-templates If you want to make it fancy use the templates. If not just use the java action to send a mail in a after create action.
Regards,
Ronald
Hi Christina,
Have a look at this how to it describes how you can send (custom) emails from your app.
With kind regards, Stephan