Auto-reply email to thank them for the subscription using the popup widget. thereby we can confirm that the email id that they have entered is valid.
Folks, our former Wishlist portal, where our users shared their requests and suggestions, was transferred to this forum. You’re most welcome to vote, add new ideas, and leave your comments here — we surely will consider them all! 
Original Votes: 2
Hello,
Thank you for submitting your idea!
I agree that it would be a good feature, and we’ll try our best to consider it for future updates.
Thanks for your help!
Hi folks,
Great news: the Auto-reply option has been added to the Popup app! 
You will find it in the Form block → Email Notifications → Notify Respondents → Autoresponder Email:
Feel free to share your feedback on feature update in the comments! 