There is an option that allows the manager to receive an email when an employee applied for an Internal Position.
1. Go to Forms > Application form > Create an application form using the custom position question type or you can edit an existing one > Select the user group who will be receiving the notification > Click Save when done.
2. Go to Admin > System notification.> Click 'My Manager (Custom Position) Notification' and create the notification that will be sent to the Manager.
3. Create an 'Internal only' job using the above application form.
4. When an internal candidate or employee applies to the job, the manager assigned user group in the application form will receive the email set up in the System notification.