You can use the custom email type in Settings > Emails to send emails to specific applicants, based on the application's category and status. Such emails can act as reminders, notifications, providing information, etc.
Simply press Add email (for Applicants) and choose Custom in the Email type setting.
Then you can choose to send the email to all Draft, Submitted, Approved, or Rejected in the Application statuses setting. You can also select specific categories to receive this email in the Application categories setting.