NoMethodError in Rails::MailersController#preview

Question

I've been receiving this error when I try to preview the my notification emails. Any ideas what might be causing it?

undefined method `html_part' for # Did you mean? html_safe?

    arel.public_send(method, *args, &block)
      else
        super
      end
    end
  end

Answer 1

I had to remove .deliver_later from the preview method.

Answer 2

The problem was there was no html rendering. Have to make sure your previews notify without error or this is the error you get.