We're sorry the mobile display of your email campaign isn't displaying line breaks the same way as it does within the desktop display, and we're here to help! Keep in mind that mobile-responsive templates use technology to adapt and format your email’s layout, based on the size of the screen it’s being displayed on. This means that the spacing (including added line breaks) can display differently. In addition, different email clients and devices have different ways of displaying email content too. A best practice is to design your email to look great on both desktop and mobile! Please click here for a helpful reference. And don't forget you'll always want to preview and send yourself a test of your email before sending it to your contacts.
I apologize at this time there is not a way to control the mobile display of your email campaign. We are however always open to ways we can better our user's experience. We have also submitted this ability as a feature request to our Product Team on your behalf. Please let us know if there is anything else we can assist with in the meantime.