Hi there @Ben_C 
Ah, I do understand your concerns and really sorry about this issue!
Indeed, popular providers like Gmail rely on advanced email sorting tools that determine what should be sent to Spam. Thus, Elfsight Form submissions may end up in Spam in some cases.
To ensure the delivery of the submissions, you should follow the steps described in our guide - Troubleshooting submissions ending up in Spam.
However, you’ve mentioned that the emails are bounced back when you are using the Autoresponder option or trying to reply to the submissions.
Could you please send me a screenshot of the error you see and a link to the page where your widget is installed? I’ll be happy to look into this for you 