AAA Form Builder gives you the option to send an autoresponder email to the person who fills your form. Follow the steps for guidance –
Step 1. Log in to your Shopify store and navigate to Apps > Form Builder.
Step 2. Create or edit a custom form.
Step 3. Navigate to Form Settings -> Emails -> Thank You Email Settings
Step 4. Toggle Reply Email field to Enable
Step 5. Customize the email as per your need. You can specify Reply-To Email, edit the email Subject and Body
User Email Template Background Color option to enable/disable the email background color.
Step 6. Once you are done customizing your email, click on the Save button