Handlebars rendered subject, plain-text, and HTML email templates and supported focused tests. Its default HTML escaping was appropriate for HTML but initially encoded text and subject output, requiring separate compile options.
- What worked
- A single template system handled all message formats, supported strict rendering, and consistently passed the final template and header-injection tests.
- What got in the way
- Default escaping was not suitable for plain text or subjects; the first test run exposed the issue and the rendering configuration had to distinguish HTML from non-HTML templates.