The "Form Auto-Responder" addon for CS-Cart, which is an auto-response email that gets automatically sent whenever a customer submits a form on your website. That can really come in handy for contact forms, support enquiries, or even custom feedback forms to let the customer know they've received the submission. 

Key Features of the Form Auto-Responder Addon

1. Automated Responses: Instantly acknowledges customer submissions, reducing wait times and improving the customer experience by sending a customised message.
2. Customisable Email Content: Tailor the response email to reflect your brand’s tone and message, and include relevant information such as expected response times or FAQs.
3. Multi-Form Compatibility: It supports all the forms that have been designed through the built-in form builder, which is rather flexible in its ability to provide various customer interaction points such as product enquiries, surveys, or event registrations. 
4. HTML and Plain Text Support: Provides support for both HTML-formatted and plain text emails to ensure compatibility with different email clients. 
5. Easy Integration with Existing Forms: Configured through the form builder to enable auto-responder functionality with minimal setup effort.
6. Multiple Recipient Options: This can auto-respond to the customer and can also be configured to send a notice to the different teams within your organisation, like sales or support. 

This addon has value to any CS-Cart-based eCommerce business if it would like to communicate with the customer effectively to improve their response time from common forms and thus create better satisfaction among customers or increase their operational efficiency. For further details, follow the documentation in CS-Cart auto-responders and form builders.