这是相关代码(C#)
                    MailMessage m;
                    SmtpClient client;   
                    client.Host = "smtp.mail.yahoo.com";
                    client.Port = 465;  
                    client.EnableSsl = true;
                    client.Credentials = new NetworkCredential("mymail@yahoo.com", "mypassword");
                    m = new MailMessage();
                    m.From = new MailAddress("mymail@yahoo.com");
                    m.To.Add(new MailAddress("anothermail@gmail.com"));
                    m.Subject = "My subject";
                    m.Body = "This is my body. ";
                    client.Send(m);
这是完整的错误跟踪
System.Net.Mail.SmtpException: Failure sending mail. ---> System.IO.IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host. ---> System.Net.Sockets.SocketException: An existing connection was forcibly closed by the remote host
   at System.Net.Sockets.Socket.Receive(Byte[] buffer, Int32 offset, Int32 size, SocketFlags socketFlags)
   at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size)
   --- End of inner exception stack trace ---
   at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size)
   at System.Net.DelegatedStream.Read(Byte[] buffer, Int32 offset, Int32 count)
   at System.Net.BufferedReadStream.Read(Byte[] buffer, Int32 offset, Int32 count)
   at System.Net.Mail.SmtpReplyReaderFactory.ReadLines(SmtpReplyReader caller, Boolean oneLine)
   at System.Net.Mail.SmtpReplyReaderFactory.ReadLine(SmtpReplyReader caller)
   at System.Net.Mail.SmtpConnection.GetConnection(ServicePoint servicePoint)
   at System.Net.Mail.SmtpTransport.GetConnection(ServicePoint servicePoint)
   at System.Net.Mail.SmtpClient.GetConnection()
   at System.Net.Mail.SmtpClient.Send(MailMessage message)
   --- End of inner exception stack trace ---
   at System.Net.Mail.SmtpClient.Send(MailMessage message)
   at EmailSender.EmailSenderForm.send() in c:\Users\Ankur\Documents\Visual Studio 2012\Projects\EmailSender\EmailSender\EmailSenderForm.cs:line 91
我在这里做错了什么?