尽管目前上网费用进行了下调，但许多网民仍认为离自己的期望还有一定距离，所以最大限度地利用电子邮件来获得各种网上信息已经成为网民上网的首选目标。邮寄目录是关于某个特殊主题的数据库，用户如果对某个主题感兴趣，可以给相关的目录服务器发电了邮件订阅，订阅得到确认 Although the current Internet costs have been reduced, but many Internet users still think they are still some distance away from their expectations, so to maximize the use of e-mail to get a variety of online information has become the preferred target for Internet users. The mailing list is a database of a particular topic, and if a user is interested in a topic, they can subscribe to the mailing list of the relevant directory server and the subscription is confirmed