Difference in sandbox and production trigger email

Hello,

I had been testing in our sandbox a trigger to send a confirmation email to anyone writing an email to my company, using dynamic content to have it available in multiple languages. While HTML formatting in the dynamic content worked in sandbox, it doesn't in production (so basically, HTML tags are visible, making it unformatted).

I have copy/pasted the exact same trigger and dynamic content from sandbox to production, yet there's that difference.

Does anyone have any idea where that could be coming from? Maybe a setting I missed somewhere?

Cheers!