No, that’s a more general question.
The creation of the email/landing page would happen on a PC/Mac with a regular web browser.
However it would be nice if you could see how the result would look like on different devices. Especially if you want to design content that looks nice on smartphones as well, you may want to take care of image size, text line brakes etc.
At the moment the person designing the email/page has to manually preview the result on a smartphone and tablet. What I was looking for is a preview function for the desktop that shows how the content would look on devices with small screens.