C#.net用QQ服务邮箱群发邮件

//winform中添加一个按钮
        private void button1_Click(object sender, EventArgs e)
        {
            //发送者邮件地址   
            string host = "[e-mail]";
            //发送者邮件开通POP3/IMAP/SMTP服务的独立密码
            string pwd = "123456";
            //接受者邮箱地址    
            string reciver = "[e-mail]";
            //SMTP服务器的主机名  
            string domainhost = "smtp.qq.com";
            //邮件标题  
            string subject = "邮件标题";
            //邮件发送的内容    
            string body = "这是邮件发送的内容";
            //调用方法，发送邮件 ,需要群发，就循环调用这个方法 ,改变接受者邮箱地址
            if (Send(host, pwd, reciver, domainhost, subject, body))
            {
                MessageBox.Show("发送邮件成功！");
            }
        }

        public bool Send(string a, string b, string c, string host, string sub, string body)
        {
            System.Net.Mail.SmtpClient client = new SmtpClient();
            client.Host = host;
            client.UseDefaultCredentials = false;
            client.Credentials = new System.Net.NetworkCredential(a, b);
            client.DeliveryMethod = SmtpDeliveryMethod.Network;
            try
            {
                System.Net.Mail.MailMessage message = new MailMessage(a, c);
                message.Subject = sub;
                message.Body = body;
                message.BodyEncoding = System.Text.Encoding.UTF8;
                message.IsBodyHtml = true;
                client.Send(message);
                return true;
            }
            catch (Exception ex)
            {
                MessageBox.Show("发送失败，原因如下:\n " + ex.Message);
                return false;
            }
        }