Hello Rushi, Thanks for this post. This seems like a combination of a support request and feature enhancement request so I'm going to remove the support part and ask that you reach out to our support for help on that portion. Regarding the showing working to confirm their email has been added to the list goes; you would typically send them to the next frame in the design on click of that submit button and on that new frame you would design and add text telling them something like "Thank you for subscribing..."

We are currently working on the ability to check a box to enable/disable allowing duplicate emails to be submitted.