JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
A possible solution I can suggest for your requirement would be to use our Submission Verifier app. Here's the link: https://apps.jotform.com/app/submission_verifier.
This app allows you to create a link that you can setup for your autoresponder. The user who receives the Autoresponder can then click that link to verify their submission. You will be notified in your email address once a user verifies their submission, which means they have opened and viewed the autoresponder email.
If you need further assistance, please let us know.