/// <summary>
        /// 邮件发送
        /// </summary>
        /// <param name="subject">邮件标题</param>
        /// <param name="body">邮件内容，html格式</param>
        /// <param name="toMailList">收件人，支持多人</param>
        /// <returns></returns>
        public async Task SendMailAsync(string subject, string body, List<string> toMailList)
        {
            try
            {
              
                SmtpClient smtpClient = new SmtpClient();
  　　　　　　　　 smtpClient.Port = 587;//默认端口25，建议不要用，阿里云和腾讯云不支持该端口
                smtpClient.DeliveryMethod = SmtpDeliveryMethod.Network;//指定电子邮件发送方式
                smtpClient.Host = "smtp.exmail.qq.com";//指定SMTP服务器
                smtpClient.Credentials = new NetworkCredential(_userName, _pwd);//用户名和密码
                smtpClient.EnableSsl = true;
                MailAddress fromAddress = new MailAddress(_userName);//用户名和密码
                MailMessage mailMessage = new MailMessage();
                mailMessage.From = fromAddress;
                toMailList.ForEach(e =>
                {
                    mailMessage.To.Add(e);
                });
                mailMessage.Subject = subject;//主题
                mailMessage.Body = body;//内容
                mailMessage.BodyEncoding = Encoding.Default;//正文编码
                mailMessage.IsBodyHtml = true;//设置为HTML格式
                mailMessage.Priority = MailPriority.Normal;//优先级
                await smtpClient.SendMailAsync(mailMessage);
            }
            catch (Exception ex)
            {
               throw ex;
            }
        }

  public static string AddEmailBody(string userName,string uPwd )
        {
            StringBuilder sbBody = new StringBuilder();
            sbBody.Append($"<div style=\"text-align:left\">感谢您使用本服务，您的登录账号已经开通：<br/>" );
            sbBody.Append($"您可使用账号：{userName}，初始密码：{uPwd}，登录URL：http://***.com<br/>");
            sbBody.Append($"用户名、密码均为重要信息，请妥善保管，不得泄露给他人，若出现信息泄露等情况，请及时联系我们。<br/></div>");
            sbBody.Append($"<div style=\"text-align:right\">{DateTime.Now.ToString("yyyy年MM月dd日")}</div>");

            return sbBody.ToString();
        }