instance method set_status

# File actionmailer/lib/action_mailer/vendor/tmail-1.2.3/tmail/port.rb, line 272
    def set_status( tag, flag )
      if m = MAIL_FILE.match(File.basename(@filename))
        s, uniq, type, info, = m.to_a
        return if type and type != '2'  # do not change anything
        newname = File.dirname(@filename) + '/' +
                  uniq + ':2,' + procinfostr(info.to_s, tag, flag)
      else
        newname = @filename + ':2,' + tag
      end

      File.link @filename, newname
      File.unlink @filename
      @filename = newname
    end