As for spam, ISPs (including mail service providers) could limit their users to, say, 100 e-mails a day; for more, you have to pay or at least post a security bond, or pass some good behavior test. At the same time, all ISPs should implement an e-mail ID system (there are two good standards, called Domain Keys and SPF).
对于垃圾邮件，ISP（包括邮件服务提供商）应该对用户发送邮件的数量有所限制，比方说，一天最多100封邮件。如果超过100封，你就要付费或通过安全测试证明是无害的。同时，ISP们应该实施一种EMAIL ID系统（目前有两个好的方法：Domain Keys和SPF），这倒不是追踪用户的邮件，而是为了防范坏人作恶。