@nebulon I tried again, and the widget worked! I saw only a simple text link because it was wrong. The correct address starts with https://. (The example code start with http:// but Mailtrain on Cloudron uses https://) After getting this worked, I'm started to want to customize the widget. (e.x. I want to use "Thank you for subscribing!" instead of the default message says "It looks like you are already subscribed to this list.") There's a file called widget-subscribe.hbs where we can customize the appearance of the widget. However, it is not accessible on Cloudron. Is(Will be) there any way to customize the widget?