Best solution for responsive email

[micker]

hello i am testing your great component ! very impressive toool
i want to create my own light newsletter builder in order to genrate html file (to send it)
i test mjml preset :

• responsive ok
• but i loose some design option (border radius, column in colum, rezizing element)
  i test newsletter preset :
• i have all design option
• but email isn't responsive (i use thunderbird insert for my testing)
  what i am doing wrong, what is the best solution ?
  regards