Assume that you try to synchronize a Microsoft Exchange ActiveSync device with a Microsoft Exchange Server 2010 mailbox by using the Exchange ActiveSync service. However, if some external URLs are not resolved on the Exchange Server 2010 Client Access server role, you cannot synchronize the device. Additionally, the following exception occurs on the Exchange server that is running the Client Access server role:
404 03FDF57B Error Number MSExchangeSync Requests ProxyHandler.BackEndGetRequestStream caught an exception
--- Exception start ---
Exception type: System.Net.WebException
Exception message: The remote name could not be resolved: 'DomainName'
Exception level: 0
Exception stack trace: at System.Net.HttpWebRequest.EndGetRequestStream(IAsyncResult asyncResult, TransportContext& context)
at System.Net.HttpWebRequest.EndGetRequestStream(IAsyncResult asyncResult)
at Microsoft.Exchange.AirSync.ProxyHandler.BackEndGetRequestStream(IAsyncResult asynchronousResult)
--- Exception end ---
--- Exception start ---
Exception type: System.Net.WebException
Exception message: The remote name could not be resolved: 'DomainName'
Exception level: 0
Exception stack trace: at System.Net.HttpWebRequest.EndGetRequestStream(IAsyncResult asyncResult, TransportContext& context)
at System.Net.HttpWebRequest.EndGetRequestStream(IAsyncResult asyncResult)
at Microsoft.Exchange.AirSync.ProxyHandler.BackEndGetRequestStream(IAsyncResult asynchronousResult)
--- Exception end ---