MailMessage message = new MailMessage();
message.To.Add("123456@qq.com");
message.From = new MailAddress("654321@qq.com");
message.Subject = "SUBJECT SUBJECT";
message.SubjectEncoding = Encoding.UTF8;
message.Body = "Body Body";
message.BodyEncoding = Encoding.UTF8;
message.IsBodyHtml = false;
message.Priority = MailPriority.Normal;
SmtpClient smtp = new SmtpClient();
smtp.Credentials = new System.Net.NetworkCredential("654321","password");
smtp.Host = "smtp.qq.com";
smtp.Port = 25;
object userState = message;
smtp.SendAsync(message,userState);
上面是代码，不知道什么问题，运行不报错，就是收不到邮件。我是用的qq邮箱发的。
检查下用户名密码端口和smtp服务器，另外你的qq邮箱是否启用了smtp
参考下这个，发邮件的核心类库不变。http://blog.csdn.net/chinacsharper/article/details/9750303
http://www.cnblogs.com/know/archive/2013/03/05/2944307.html
http://www.360doc.com/content/13/0809/08/10504424_305765275.shtml
你不要异步send了 直接send呢？
密码那里要填写授权码