If you're new to creating Email Widgets, Please check out this tutorial on how to create and style email widgets.
All static email UGC widgets are compatible with Rule
Static email widgets
Once you have created and styled your email UGC widget, click Embed widget
Select your market in the dropdown
Click Copy to copy the whole embed code
Navigate to your Email in Rule
In a text block, click < > Källa / Source
Paste your embed code
Click OK
Done 🎉 Your email UGC widget is now visible in the preview.