You can set a global doctype to be used by all your email templates:

// config.js
module.exports = {
  doctype: 'html',
  // ...

You then reference this in your master Layout, from the page object:

<!DOCTYPE {{ page.doctype or 'html' }}>

Just like above, you can fallback to a default value with Nunjucks templating logic.

Front Matter

You can also use Front Matter, to set the doctype locally instead of globally.

For example, let's create src/templates/old.njk and use a Transitional doctype for it:

doctype: html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" ""

{% block template %}
  <!-- ... -->
{% endblock %}


The default Layout in the Starter will fallback to an HTML5 doctype. It's the shortest, and it's enough to trigger standards mode.