# File lib/mail/message.rb, line 1660
    def add_file(values)
      convert_to_multipart unless self.multipart? || self.body.decoded.blank?
      add_multipart_mixed_header
      if values.is_a?(String)
        basename = File.basename(values)
        filedata = File.open(values, 'rb') { |f| f.read }
      else
        basename = values[:filename]
        filedata = values[:content] || File.open(values[:filename], 'rb') { |f| f.read }
      end
      self.attachments[basename] = filedata
    end