try             {                 MailMessage mm = new MailMessage();                 MailAddress Fromma = new MailAddress("xxxx@qq.com");                 MailAddress Toma = new MailAddress("MMMMMMM@qq.com", null);                 mm.From = Fromma;                 //收件人                 mm.To.Add("MMMMMM@qq.com");                 //邮箱标题                 mm.Subject = "Hello Dear:";                 mm.IsBodyHtml = true;                 //邮件内容                 mm.Body = "你好Mr流星！";                 //内容的编码格式                 mm.BodyEncoding = System.Text.Encoding.UTF8;                 //mm.ReplyTo = Toma;                 //mm.Sender =Fromma;                 //mm.IsBodyHtml = false;                 mm.DeliveryNotificationOptions = DeliveryNotificationOptions.OnSuccess;                 mm.CC.Add(Toma);                 SmtpClient sc = new SmtpClient();                 NetworkCredential nc = new NetworkCredential();                 nc.UserName = "XXXXX@qq.com";//你的邮箱地址                 nc.Password = "zzzzz";//你的邮箱密码,这里的密码是xxxxx@qq.com邮箱的密码，特别说明下~                    sc.UseDefaultCredentials = true;                 sc.DeliveryMethod = SmtpDeliveryMethod.Network;                 sc.Credentials = nc;                 //如果这里报mail from address must be same as authorization user这个错误，是你的QQ邮箱没有开启SMTP，                 //到你自己的邮箱设置一下就可以啦！在帐户下面,如果是163邮箱的话，下面该成smtp.163.com                 sc.Host = "smtp.qq.com";                 sc.Send(mm);             }             catch (Exception ex)             {                 throw new Exception(ex.Message);             }