Currently the email editor seems to use an old editor version which only supports inline heml style and not css, since only the is editable.

Since this functionality is already implemented in Customer Insights Email Template editor that provides responsive design and drag n drop feature, it could be very usefull:

• to have the same editor in Customer Voice or at least
• for Customer Voice editor to understand the Customer Insights editor's output

This need is very important because customer voice refers to customers and in order to provide the best user experience we need the most recent designing tools like the one in Customer Insights Email Template