Here are the troubleshooting steps if your email action configured with the default email id is not getting delivered to the intended users
First, check the logs screen in ARN and see the status of your ARN email rule.
If the rule execution status in logs is ‘Failure’ click on the status to see the exact reason for the failure.
If the rule execution status in logs is ‘Success’, then it means the app did send out the email.
Now if the email isn't received, the problem could lie with the email receiver's service provider. Most likely, the email receiver server is blocking that email. The simple way to verify this is to include a personal email address in the list and then execute the ARN rule. If the personal email address receives the email, then that means the app is generating emails properly.