Which Email-module?
In most of the modules: By calling the SendMail-microflow.
You can add an "on change" event on the radio button, for example, a microflow, the parameter of the microflow will be the object of the data source, you need to check the value of the boolean attribute that links to the radio button. In the true path, you need to build a logic for sending email depending on the email module you use in the project.