Hi @NCondon22,
I don’t think there is a reliable way to achieve this and I would always lean towards simply asking for the email address again. The risk for error is simply too high and I’ve seen to many HubSpot users try this against recommendations not to do so and then being faced with contact records that apparently were mixed up.
The parameters added to a URL by, using a personalization token, e.g. ACME Laboratories{{ contact.email }} would work. Yes, you would be including personal information in the email but in this case, it would already be included as it’s the recipient?
In any case, I would not make it a hidden field just in case the parameter is stripped away – by privacy extensions or users, you never know.
Beyond that, HubSpot forms are simply not a tool that can accomplish this reliably. With the pre-filled forms feature, a forwarded email can ruin everything: Understand pre-populated form fields
With the query string, you’d include information about the recipient in the email: Auto-populate form fields with a query string
Best regards!