说明：  利用System.Web.Mail这个名称空间.在这个名字空间下，有一个专门使用SMTP协议来发送邮件的类：SmtpMail,它已能满足最普通的发送邮件的需求。这个类只有一个自己的公共函数--Send()和一个公共属性—SmtpServer，您必须通过SmtpServer属性来指定发送邮件的服务器的名称（或IP地址）,然后再调用Send()函数来发送邮件。您可以在Send函数的参数MailMessage对象中设置邮件的相关属性，如优先级、附件等等。除了以MailMessage对象为参数（如上述代码），Send函数还可以简单的直接以邮件的4个主要信息（from，to，subject，messageText）作为字符串参数来调用。
(The use of System.Web.Mail namespace. In the name space, there is a special SMTP protocol used to send the message class: SmtpMail, it has been able to send messages to meet the most common needs. This class is only one of their public functions- Send () and a public property-SmtpServer, you must SmtpServer attribute to specify the sending mail server' s name (or IP address), and then call the Send () function to send a message. Send function, you can set the parameters of MailMessage object mail-related properties, such as priority, accessories and more. In addition to the MailMessage object as an argument (such as the above code), Send function, you can simply e-mail directly to the 4 key messages (from, to, subject, messageText) as a string parameter to call.)