# File lib/vmail/imap_client.rb, line 601
    def append_to_file(uid_set, file)
      uid_set = uid_set.split(',').map(&:to_i)
      log "append to file uid set #{uid_set.inspect} to file: #{file}"
      uid_set.each do |uid|
        message = show_message(uid)
        File.open(file, 'a') {|f| f.puts(divider('=') + "\n" + message + "\n\n")}
        subject = (message[/^subject:(.*)/,1] || '').strip
        log "appended message '#{subject}'"
      end
      "printed #{uid_set.size} message#{uid_set.size == 1 ? '' : 's'} to #{file.strip}"
    end