@Liam_Austin, without the use of a script on the page where your form code resides and passing the details as URL parameters from the email link, the only native way to pass details to a form is to either use an Infusionsoft hosted form or the Javascript version.
Ah, it’s only for one form…understandable you wouldn’t want a 3rd party for just one. The new landing page builder is now able to pass contact fields and use hidden fields for the email so that they don’t change their email and create a duplicate record…I see you’re trying it. Will that work for you?