SmtpClient client = new SmtpClient();
            client.Host = SmtpHost;
            client.EnableSsl = true;  //Error: need EHLO and AUTH first
            client.UseDefaultCredentials = true;
            client.Credentials = new System.Net.NetworkCredential(SendEmail, SendEmailPwd);
            client.DeliveryMethod = SmtpDeliveryMethod.Network;

            MailMessage message = new MailMessage();
            //发件人
            MailAddress addressFrom = new MailAddress(SendEmail, SendEmail);
            message.From = addressFrom;
            
            //收件人
            paraRecipientEmails = paraRecipientEmails.Replace("；", ";");
            String[] recipients = Regex.Split(paraRecipientEmails, ";", RegexOptions.IgnoreCase);
            foreach (String recipient in recipients)
            {
                MailAddress recipientEmail = new MailAddress(recipient);
                message.To.Add(recipientEmail);
            }
            //邮件标题
            message.Subject = paraSubject;
            //邮件内容
            message.Body = paraBody;
            //邮件编码
            message.BodyEncoding = System.Text.Encoding.UTF8;
            //是否为HTML格式
            message.IsBodyHtml = true;
            //至少有一个收件人
            if (message.To.Count > 0)
            {
                client.Send(message);
            }