类sendemail中的方法 

public bool send(string toadd, string sb, string subject)
    {
        try
        {
            MailAddress from = new MailAddress("xxx@163.com");
            MailAddress to = new MailAddress(toadd);

            MailMessage message = new MailMessage(from, to);
            message.Subject = subject;
            message.IsBodyHtml = true;

            message.Body = sb;
            SmtpClient client = new SmtpClient("smtp.163.com");
            client.Credentials = new System.Net.NetworkCredential("xxx@163.com", "邮箱密码");
            client.Send(message);
            message.Dispose();
            return true;

        }
        catch { return false; }
    }

事件

 protected void sumbit_ServerClick(object sender, EventArgs e)
    {
         sendmassage send = new sendmassage();
         bool i=send.send("xx@qq.com", "测试", "成功否？");
         if (i == true)
         { Label1.Text = "发送成功！"; }
         else { Label1.Text = "出错了"; }

    }