//下面开始敲代码。。。

//两个命名空间

//using System.Net;
//using System.Net.Mail;

/// <summary>
/// 发送验证码按钮
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
protected void Button1_Click(object sender, EventArgs e)
{
//随机验证码
Random rm = new Random();
int i;
string str = string.Empty;
for (int p = 0; p < 6; p++)
{
i = Convert.ToInt32(rm.NextDouble() * 10);
str += i;
}
string content ="**科技提醒您：您正在使用去圈创邮箱安全验证服务，您本次操作的验证码是："+str
SendEmail1("1208240949@qq.com", "【**科技】后台登录修改用户信息提示", content);//收件人邮箱，邮箱标题，邮箱内容
}
#region
/// <summary>
/// 发送邮箱
/// </summary>
/// <param name="mailTo">收件人</param>
/// <param name="mailSubject">标题</param>
/// <param name="mailContent">内容</param>
/// <returns></returns>
public static void SendEmail1(string mailTo, string mailSubject, string mailContent)
{
SmtpClient mailClient = new SmtpClient("smtp.qq.com");
mailClient.EnableSsl = true;
mailClient.UseDefaultCredentials = false;
//Credentials登陆SMTP服务器的身份验证.
mailClient.Credentials = new NetworkCredential("1208240907@qq.com", "aaaaaaaaaaaa");//邮箱，
MailMessage message = new MailMessage(new MailAddress("1208240907@qq.com"), new MailAddress(mailTo));//发件人，收件人
message.IsBodyHtml = true;
// message.Bcc.Add(new MailAddress("tst@qq.com")); //可以添加多个收件人
message.Body = mailContent;//邮件内容
message.Subject = mailSubject;//邮件主题
//Attachment 附件
//Attachment att = new Attachment(@"C:/hello.txt");
//message.Attachments.Add(att);//添加附件
//Console.WriteLine("Start Send Mail....");
//发送....
mailClient.Send(message); // 发送邮件
}
#endregion
/// <summary>
/// 验证验证码按钮
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
protected void Button2_Click(object sender, EventArgs e)
{
if (TextBox1.Text.Trim() == Session["Rom"].ToString())
{
Page.ClientScript.RegisterClientScriptBlock(Page.ClientScript.GetType(), "myscripts", "<script>alert(\"验证成功!\");</script>");
}
else
{
Page.ClientScript.RegisterClientScriptBlock(Page.ClientScript.GetType(), "myscripts", "<script>alert(\"验证失败!\");</script>");
}
}

然后运行