Install the plugin, activate it and the plugin window shows all our themes installed in WordPress. Select the files from main theme to duplicate how child theme and it’s ready. In a few seconds we have created and working perfectly. You will be able to make all the changes that you like.
Other way to do that is using the small plugin WP SMTP MAIL, that gets the same which gets the same as the previous code, setting the email account to use besides. It also allows a test to see if the plugin works correctly and , if not, it launch a code where we can study the problem.