子域创建的用户，访问
OWA提示找不到子域
Request
Url:
User host address: 36.248.226.170
Exception
Exception type: Microsoft.Exchange.Data.Directory.ADTransientException
Exception message: Could not find any available Domain Controller in domain DC=xx,DC=xx,DC=COM.
Call stack
在 Microsoft.Exchange.Data.Directory.DSAccessTopologyProvider.GetServerFromDomainDN(String distinguishedName, NetworkCredential credential) 在 Microsoft.Exchange.Data.Directory.ConnectionPoolManager.GetConnection(ConnectionType connectionType, ADObjectId domain, String serverName, Int32 port, NetworkCredential credential) 在 Microsoft.Exchange.Data.Directory.ConnectionPoolManager.GetConnection(ConnectionType connectionType, NetworkCredential networkCredential, ADObjectId domain) 在 Microsoft.Exchange.Data.Directory.ADSession.GetConnection(String preferredServer, Boolean isWriteOperation, Boolean isNotifyOperation, ADObjectId& rootId) 在 Microsoft.Exchange.Data.Directory.ADSession.GetReadConnection(String preferredServer, ADObjectId& rootId) 在 Microsoft.Exchange.Data.Directory.ADSession.Find(ADObjectId rootId, String optionalBaseDN, ADObjectId readId, QueryScope scope, QueryFilter filter, SortBy sortBy, Int32 maxResults, IEnumerable`1 properties, CreateObjectDelegate objectCreator, CreateObjectsDelegate arrayCreator) 在 Microsoft.Exchange.Data.Directory.ADSession.Read(ADObjectId entryId, IEnumerable`1 properties, CreateObjectDelegate objectCtor) 在 Microsoft.Exchange.Data.Directory.Recipient.ADRecipientSession.Read(ADObjectId entryId) 在 Microsoft.Exchange.Data.Storage.ExchangePrincipal.Save() 在 Microsoft.Exchange.Clients.Owa.Core.RequestDispatcher.DispatchLanguagePostLocally(OwaContext owaContext, OwaIdentity logonIdentity, CultureInfo culture, String timeZoneKeyName, Boolean isOptimized) 在 Microsoft.Exchange.Clients.Owa.Core.RequestDispatcher.DispatchLanguagePostRequest(OwaContext owaContext) 在 Microsoft.Exchange.Clients.Owa.Core.RequestDispatcher.PrepareRequestWithoutSession(OwaContext owaContext, UserContextCookie userContextCookie) 在 Microsoft.Exchange.Clients.Owa.Core.RequestDispatcher.InternalDispatchRequest(OwaContext owaContext) 在 Microsoft.Exchange.Clients.Owa.Core.RequestDispatcher.DispatchRequest(OwaContext owaContext) 在 System.Web.HttpApplication.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() 在 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)
这个会是什么
问题，求解？其他子域不会有这样的问题。
