SmtpClient smtpClient = new SmtpClient();

            smtpClient.DeliveryMethod = SmtpDeliveryMethod.Network;//指定電子郵件傳送方式

            smtpClient.Host = "";//指定SMTP伺服器

            smtpClient.Credentials = new NetworkCredential("", "");//使用者名稱和密碼

            smtpClient.EnableSsl = true;

            MailAddress fromAddress 
 
= new MailAddress("fromMail", "nickName");

            MailAddress toAddress = new MailAddress("toMail");

            MailMessage mailMessage = new MailMessage(fromAddress, toAddress);

            mailMessage.Subject = "";//主題

            mailMessage.Body = "";//內容

            mailMessage.BodyEncoding 
 
= Encoding.Default;//正文編碼

            mailMessage.IsBodyHtml = true;//設定為HTML格式

            mailMessage.Priority = MailPriority.Normal;//優先順序

            smtpClient.SendMailAsync(mailMessage);