c#实现的邮件发送系统，有详细的使用说明书，包括邮件发送，重新登录、邮件群发、添加好友、查看好友、查看邮件信息、查看紧急邮件等模块组成-c# achieve the mail delivery system, a detailed manual, including mail send,relogin, bulk mail, add friends, view friends, view e-mail messages, view an urgent message other modules