The Acknowledge email will notify the applicant that his/her application has been reviewed, which helps keep applicants engaged throughout the screening/hiring process. Below is a copy of the standard Acknowledge email that comes with your hiring site.
Dear John Snow,
Your job application for the Customer Service Manager position has now moved to the evaluation stage. If you are selected for an interview, you will receive an email (and text message if you opted in) with specific scheduling instructions.
If you are no longer interested in this job and want to withdraw your application from consideration, please click withdraw.
The Hiring Manager