The request failed. The underlying connection was closed: An unexpected error occurred on a receive (4301766)

Mage Agent reports the following error

2018-01-30 16:57:47.4005 Px166C Tx11 A160 C97 M834 Error Microsoft.Exchange.WebServices.Data.ServiceRequestException: The request failed. The underlying connection was closed: An unexpected error occurred on a receive. |    at Microsoft.Exchange.WebServices.Data.ServiceRequestBase.GetEwsHttpWebResponse(IEwsHttpWebRequest request)
   at Microsoft.Exchange.WebServices.Data.ServiceRequestBase.ValidateAndEmitRequest(IEwsHttpWebRequest& request)
   at Microsoft.Exchange.WebServices.Data.MultiResponseServiceRequest`1.Execute()
   at Microsoft.Exchange.WebServices.Data.ExchangeService.InternalBindToFolders(IEnumerable`1 folderIds, PropertySet propertySet, ServiceErrorHandling errorHandling)
   at Microsoft.Exchange.WebServices.Data.ExchangeService.BindToFolder(FolderId folderId, PropertySet propertySet)
   at Microsoft.Exchange.WebServices.Data.ExchangeService.BindToFolder[TFolder](FolderId folderId, PropertySet propertySet)
   at Quest.MigrationManager.Exchange.MigrationConnectors.Ews.ProductionExchangeService.FolderBind(WellKnownFolderName name, PropertySet propertySet)
   at Quest.MigrationManager.Exchange.MigrationConnectors.Ews.EwsSyncConnector.ConnectInternal()
   at Quest.MigrationManager.Exchange.MigrationConnectors.Ews.EwsSyncConnector.Connect()
[inner] System.Net.WebException: The underlying connection was closed: An unexpected error occurred on a receive. |    at System.Net.HttpWebRequest.GetResponse()
   at Microsoft.Exchange.WebServices.Data.EwsHttpWebRequest.Microsoft.Exchange.WebServices.Data.IEwsHttpWebRequest.GetResponse()
   at Microsoft.Exchange.WebServices.Data.ServiceRequestBase.GetEwsHttpWebResponse(IEwsHttpWebRequest request)
[inner] System.IO.IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host. |    at System.Net.Security._SslStream.EndRead(IAsyncResult asyncResult)
   at System.Net.TlsStream.EndRead(IAsyncResult asyncResult)
   at System.Net.PooledStream.EndRead(IAsyncResult asyncResult)
   at System.Net.Connection.ReadCallback(IAsyncResult asyncResult)
[inner] System.Net.Sockets.SocketException: An existing connection was forcibly closed by the remote host |    at System.Net.Sockets.Socket.EndReceive(IAsyncResult asyncResult)
   at System.Net.Sockets.NetworkStream.EndRead(IAsyncResult asyncResult)

This error can have many causes in the customer environment but may be caused by Load Balancing appliances or an Environmental issue.

In one case it was found that the problem mailboxes were in a Datacenter that was behind a Firewall (NAT).

Once the mailboxes were moved to another datacenter that was not protected by this method, Synchronization and Switching was successful.