In the Org & Brand Console (/admin/organization/brand), turn on the automatic reply in the candidate settings and write the message. It can greet the candidate by first name with {{FIRST_NAME}}, and it is sent the moment an application is submitted.
It is idempotent: a candidate who re-submits does not receive it twice.
This reply is separate from the status e-mails the pipeline sends when you move an application — see "Which status changes e-mail the candidate".
Ready to see it in your own console?
Posting and reviewing are free. Every stage, e-mail and export described here is in the console from the first sign-in.