You can automatically send an email to anyone who submits a form, just to confirm that you've received it. This is disabled by default, so to enable it, from the main Dashboard, click the “cog” icon to start editing the form.
Scroll down to the Autoresponder section and click to enable it.
Now click on the Configure button.
Make sure the Field name is set to the name of the field on your form where the user enters their email address then update the other fields to whatever you want.
The Body field will accept any valid Markdown syntax. Check out the Markdown Guide for more information. You can preview what your message will look like by clicking on the "Preview" button.