i asked myself the same question two or three weeks ago. no, there are no seals, the water will drop down into the door and then out through the holes in the bottom. My inside of the doors is rusty (Fordor) so we will be dry-ice cleaning the inside and then cover the metal with some rubber-type material to prevent any oxygen to get to the surface again.
My question is: do i have to do the same process with the area behind the doors? so, by the side of the rear passenger seats und the window that's behind the doors (it's a three window Fordor). From FordBarns experience, does that rust just like the inside of the doors?