There are two methods used in email development industry:
- with CSS Media Queries use, let's call it “Responsive”;
- without Media Queries, or "Fluid-hybrid."
The actual problem is that some mobile email applications still don’t support responsive layout.
We are aware of this problem and even published a dedicated post.
So what happens when exporting? You click the Export button, email is sent right to the desired service - and if there’s no responsive layout support, all the media styles are automatically removed making it not responsive for mobile clients.
Unfortunately, there is no way to fix it as these things are not under our control.