Using WooCommerce Email Template Customizer email are not responsive on mobile

I’ve encountered an issue with the WooCommerce Email Template Customizer plugin.

The problem arises when viewing emails on mobile devices that are sent through the plugin. While editing the email template in the backend and simulating mobile viewing, everything appears fine. However, after sending a test email using the customized template and checking on a mobile device, the email is displayed in the same format as on a PC.

In summary, my concern is that the email templates are not responsive when viewed on smartphones, despite the responsive design being simulated during the editing process.