Hi Sydney,
Although Marketo is supposed to autopopulate forms even when a user clicks a link in an email for the first time, we found that this wasn't always the case when we did extensive testing. We may have been a unique case, however, because all of our forms at this point were iframed into our web site and we suspected that this may have been the culprit. Note: if you do this remember to add the Marketo Javascript code to the headers of your Web Site so that it passes the marketo token down to the iframed page.
The solution we came up that seemed to work in our specific scenario was to build a second marketo landing page that redirects to the page on our web site that contains the iframed Marketo form. This idea here was that we thought Marketo wouldn't have enough time to ID the person before the form was being called in by the iframed page and by adding that one extra redirect Marketo had time to get the cookie on the users machine,then when the page was loaded, to serve up the prefilled content.
Sydney, in your specific case I would recommend that you start by testing. Test computers that have not been used yet with a Marketo enabled form or clicked a link from a Marketo sent email. Send a user a Marketo email with a link to your form and see if it autopopulates for them. in our testing we found that before the solution we implemented, the form was never prefilled for first time visitors, but that the solution solved the problem in 10/10 cases. We used email account of other staff in our department and personal emails/personal devices.
Good luck!
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