If you wish to customize the design and display of the Master, Portal, or Child GUI interfaces, you may edit the custom CSS files. The files are listed here:
/usr/lib/mailborder/web_assets/css/master_custom.css /usr/lib/mailborder/web_assets/css/portal_custom.css /usr/lib/mailborder/web_assets/css/child_custom.css
There are also softlinks to the respective files in the /etc/mailborder/directory