C#发送电子邮件

            string send = txtSend.Text.Trim();//发件人邮箱地址
            string to = txtTo.Text.Trim();//收件人邮箱地址
            if (regex(send) && regex(to))//判断发件人邮箱地址&&收件人邮箱地址不为空
            {
                if (send != "" && to != "" && txtpwd.Text != "")
                {
                    DialogResult result = MessageBox.Show("确认发送", "系统提示", MessageBoxButtons.OKCancel, MessageBoxIcon.Information);
                    if (result == DialogResult.OK)
                    {
                        try
                        {
                            MailMessage mailMessage = new MailMessage();
                            mailMessage.From = new MailAddress(send);//发件人邮箱地址
                            mailMessage.To.Add(new MailAddress(to));//收件人邮箱地址
                            mailMessage.Subject =Convert.ToBase64String(Encoding.UTF8.GetBytes(txtSubject.Text));//对邮件主题进行编码
                            mailMessage.Body = Convert.ToBase64String(Encoding.UTF8.GetBytes(rtboxContent.Text));//对邮件内容进行编码
                            SmtpClient client = new SmtpClient();
                            client.Host = "smtp." + send.Substring(send.IndexOf("@") + 1);//邮箱的服务器的地址
                            client.EnableSsl = true;//是否加密连接
                            client.UseDefaultCredentials = false;//不和请求一起发送
                            client.Credentials = new NetworkCredential(send, txtpwd.Text);//验证发件人的身份
                            client.Send(mailMessage);//发送邮件
                            MessageBox.Show("发送成功", "系统提示", MessageBoxButtons.OK, MessageBoxIcon.Information);
                        }
                        catch
                        {
                            MessageBox.Show("发送失败", "系统提示", MessageBoxButtons.OK, MessageBoxIcon.Error);
                        }
                    }
                }
                else
                {
                    MessageBox.Show("发件人邮箱、发件人密码、收件人邮箱不能为空！", "系统提示", MessageBoxButtons.OK, MessageBoxIcon.Hand);
                }
            }
            else
            {
                MessageBox.Show("请输入正确的电子邮件", "系统提示", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }