解决方法,加上红色部分就可以了.

       /// <summary>
        /// 发送Email
        /// </summary>
        /// <param name=""userEmail""></param>
        private void SendEmail(string body)
        {
            MailMessage mm = new MailMessage(FROMEMAIL, MANAGEREMAIL);
            SmtpClient sc = new SmtpClient("smtp.gmail.com");
            sc.UseDefaultCredentials = false;
            sc.Credentials = new System.Net.NetworkCredential(PERMIT, EMAILPWD);
            sc.EnableSsl = true;
            sc.DeliveryMethod = SmtpDeliveryMethod.Network;
            mm.Subject = SUBJECT;
            mm.IsBodyHtml = true;
            mm.BodyEncoding = System.Text.Encoding.UTF8;
            mm.Body = body;
            sc.Send(mm);
        }