Is there a way to append a token or something to the URL for a landing page so that it automatically prefills a form with an email address? I am sending a 3rd party email that takes a user to a landing page, and I know that if they are cooked in Marketo the form will prefill, but is there a way to have the form prefill if they're not already cookied/in the Marketo database?
This might help you - Set a Hidden Form Field Value - Marketo Docs - Product Docs . Sounds like a hidden field that's autofilled from UTM parameter will be what you're looking for. Depending on the third party's data, they may be able to input token-type into that's specific to each individual user (like email address), but generic campaign specific values would also work.
In addition to Grace's note on hidden fields to track on form fillout, you can also consider tracking the clicks themselves: http://blog.teknkl.com/tracking-clicks-non-marketo-emails/