# File lib/vmail/message_formatter.rb, line 13
    def list_parts(parts = (@mail.parts.empty? ? [@mail] : @mail.parts))
      if parts.empty?
        return []
      end
      lines = parts.map do |part|
        if part.multipart?
          list_parts(part.parts)
        else
          # part.charset could be used
          "- #{part.content_type}"
        end
      end
      lines.flatten
    end