collect_responses_from_templates

# File actionmailer/lib/action_mailer/base.rb, line 992
      def collect_responses_from_templates(headers)
        templates_path = headers[:template_path] || self.class.mailer_name
        templates_name = headers[:template_name] || action_name

        each_template(Array(templates_path), templates_name).map do |template|
          format = template.format || self.formats.first
          {
            body: render(template: template, formats: [format]),
            content_type: Mime[format].to_s
          }
        end
      end