code: function render (template, locals, callback) {
    var engineExt =
    engineName.charAt(0) === '.' ? engineName : ('.' + engineName)
    var tmplPath = path.join(templatesDir, template + engineExt)
    var origTmplPath = path.join(origTemplatesDir, template + engineExt)
  
    function renderToText (html) {
      var text = htmlToText.fromString(html, {
        wordwrap: 72 // A little less than 80 characters per line is the de-facto
      // standard for e-mails to allow for some room for quoting
      // and e-mail client UI elements (e.g. scrollbar)
      })
  
      callback(null, html, text)
    }
  
    engine(tmplPath, locals)
      .then(renderToText)
      .catch(function () {
        engine(origTmplPath, locals)
          .then(renderToText)
          .catch(function (err) {
            callback(err)
          })
      })
  }
docs: Render e-mail templates to HTML and text