The email address we send our Marketo campaigns from is a custom mailbox on our server that I only have access to. I create/design the email - I send myself a "Test" of course to verify, when all is good, I schedule the send to the list as required. There is no forwarding, no link adjustments. The email is an original for everyone, yet when one person clicks on the link to go to the landing page, some see info for someone who has already filled out the form at a completely different company.