You can set up a trigger-based smart campaign (make this a local asset in your program) to watch for a form submit from any member of the out-bound campaign where you sent the email out...Just say filled out form "not unsuscribe".
Also remeber to link your program to a SFDC campaign is the set up tab. This is wil give you what you need for multi-touch atribution, as this lead took multiple touchs to convert.