底层连接已关闭:在发送时发生意外错误

我有一个用[c#]编写的windows Service例程。. Net使用VS 2010，每天访问一次数据库，如果有任何记录需要处理。将通过Exchange服务器向这些记录所有者发送电子邮件。对于前几条记录，电子邮件发送得很好，但在第4或第5封电子邮件之后，我得到了一个错误，如show

Service failed at :System.Net.WebException: The underlying connection was closed: An unexpected error occurred on a send. ---> 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.FixedSizeReader.ReadPacket(Byte[] buffer, Int32 offset, Int32 count)
   at System.Net.Security.SslState.StartReceiveBlob(Byte[] buffer, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.CheckCompletionBeforeNextReceive(ProtocolToken message, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.StartSendBlob(Byte[] incoming, Int32 count, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.ForceAuthentication(Boolean receiveFirst, Byte[] buffer, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.ProcessAuthentication(LazyAsyncResult lazyResult)
   at System.Net.TlsStream.CallProcessAuthentication(Object state)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Net.TlsStream.ProcessAuthentication(LazyAsyncResult result)
   at System.Net.TlsStream.Write(Byte[] buffer, Int32 offset, Int32 size)
   at System.Net.PooledStream.Write(Byte[] buffer, Int32 offset, Int32 size)
   at System.Net.ConnectStream.WriteHeaders(Boolean async)
   --- End of inner exception stack trace ---
   at System.Net.HttpWebRequest.GetResponse()
   at Microsoft.Exchange.WebServices.Data.ServiceRequestBase.Emit(HttpWebRequest& request)
   at Microsoft.Exchange.WebServices.Data.ServiceRequestBase.ValidateAndEmitRequest(HttpWebRequest& request)

如果我用断点调试例程，它工作得很好。但是当我在没有任何断点的情况下运行它时，我会得到上面的错误。下面是我的例程发送电子邮件的代码片段:

ExchangeService service = new ExchangeService(ExchangeVersion.Exchange2010_SP1);
lock (service)
{
   if (service == null)
      throw new Exception("service is null");
   service.Credentials = new WebCredentials(data[0], data[1]);
   service.Url = new Uri("https://owa.CompanyName.com/ews/exchange.asmx");
   service.Timeout = 1200000;
   EmailMessage message = new EmailMessage(service);
   if (message == null)
       throw new Exception("message is null");
       message.Subject = "Test Email";
       message.Body = "This is a Test EMail Please use the below link to update ";
//message.ToRecipients.Add(docList[0].CreatorEmailID);
       message.ToRecipients.Add("EmailID@gmail.com");
       for (int j = 0; j < emailList.Count; j++)
       {
          message.CcRecipients.Add("EmailID@gmail.com”);
       }
       System.Threading.Thread.Sleep(1000);
       ServicePointManager.ServerCertificateValidationCallback += ignoreCertCallback;
       try
       {
        message.Send();
       }
       finally
       {
       ServicePointManager.ServerCertificateValidationCallback -= ignoreCertCallback;
       }
}

我在这里使用Microsoft Exchange WebService作为web参考。我试着在谷歌上搜索，但它并没有真正帮助我。如果有人能在这个问题上帮助我，我将非常高兴。