One approach towards reducing electronic junk, including spam in e-mail and on the Web, is to assign a small cost to the act of sending mail, or posting information on a Web site.
减少电子垃圾（包括电子邮件和 Web 上的垃圾信息）的一种方式是给发送邮件或在 Web 站点发布信息的行为加上一些成本。
2
The E-Mail system should prevent the hacker's attack, will prevent the junk email from overflowing, avoid the letting out of materials content of the sensitive mail at the same time.
电子邮件系统既要防止黑客的攻击，还要防止垃圾邮件泛滥，同时要避免敏感邮件资料内容的泄漏。
3
With the wide application of E-mail, all kinds of junkmail or virus have invaded the E-mail system, serious impacting on it's common using.