说明：  email整个电子邮件系统由服务器程序和客户端程序两大部分组成。服务器程序由两大模块组成：通信模块和服务器文件处理模块；客户端程序也由两大模块组成：通信模块和界面提供模块。
(email the entire e-mail system by the server and client procedures of two major components. Server program module by the two major components: communication module and server document processing module client module from the two major components: communication modules and interface modules.)