Ok so as I work through this I will share my findings.
Heres my general set up and a finding pointing to the actual domain sending to sendy.
I own
Carsonfootwear.com
Rbl-Marketing.com
Pdxenvelope.com
I have the sendy set up at razzel.us its a stand alone hosted on cloadways.
I think Sendy will only communicate with the url it was purchased under
RBL-Marketing.com so I need to build all landing pages on/withing that domain for the data to transfer? Question is if I am to roll this out to multiple clients how do I do that clients will not want rbl showing up on there landing page??