Your software
My Mautic version is: 4.1.0
My PHP version is: 7.4
My Database type and version is: MySQL 8+
Your problem
My problem is:
I created a mjml template but it seems that the full-width=“full-width” attribute for section / wrapper is either not working or ignored.
MJML “Try It Live” shows that it’s a functional attribute
Just create the email you want with mjml outside of Mautic and upload it into mautic as a theme.
It may not still render correctly in Mautic but if you send off the email like a test email, you’ll received it correctly rendered as you developed it in mjml.