I have this error but only with some mailboxes... should be to this? Request Url: https://srvexchange:443/owa/default.aspx User host address: 10.1.1.118 Exception Exception type: Microsoft.Exchange.Data.Storage.ConnectionFailedTransientException Exception message: Cannot open mailbox /o=Bancontinental/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=cbgustavo. Call stack en Microsoft.Exchange.Data.Storage.ConnectionCachePool.OpenMailbox(String serverDn, String userDn, String mailboxDn, Guid mailboxGuid, Guid mdbGuid, Object identity, ConnectFlag connectFlag, OpenStoreFlag openStoreFlag, CultureInfo cultureInfo, String clientInfoString, Boolean secondTry) en Microsoft.Exchange.Data.Storage.ConnectionCachePool.OpenMailbox(String serverDn, String userDn, String mailboxDn, Guid mailboxGuid, Guid mdbGuid, Object identity, ConnectFlag connectFlag, OpenStoreFlag openStoreFlag, CultureInfo cultureInfo, String clientInfoString, Boolean secondTry) en Microsoft.Exchange.Data.Storage.ConnectionCachePool.OpenMailbox(String serverDn, String userDn, String mailboxDn, Guid mailboxGuid, Guid mdbGuid, Object identity, ConnectFlag connectFlag, OpenStoreFlag openStoreFlag, CultureInfo cultureInfo, String clientInfoString) en Microsoft.Exchange.Data.Storage.MailboxSession.Initialize(LogonType logonType, ExchangePrincipal owner, DelegateLogonUser delegateUser, Object identity, OpenMailboxSessionFlags flags) en Microsoft.Exchange.Data.Storage.MailboxSession.CreateMailboxSession(LogonType logonType, ExchangePrincipal owner, DelegateLogonUser delegateUser, Object identity, OpenMailboxSessionFlags flags, CultureInfo cultureInfo, String clientInfoString) en Microsoft.Exchange.Data.Storage.MailboxSession.Open(ExchangePrincipal mailboxOwner, WindowsPrincipal authenticatedUser, CultureInfo cultureInfo, String clientInfoString) en Microsoft.Exchange.Clients.Owa.Core.OwaWindowsIdentity.CreateMailboxSession(ExchangePrincipal exchangePrincipal, CultureInfo cultureInfo) en Microsoft.Exchange.Clients.Owa.Core.UserContext.Load(OwaContext owaContext) en Microsoft.Exchange.Clients.Owa.Core.RequestDispatcher.CreateUserContext(OwaContext owaContext, UserContextKey userContextKey, UserContext& userContext) en Microsoft.Exchange.Clients.Owa.Core.RequestDispatcher.PrepareRequestWithoutSession(OwaContext owaContext, UserContextCookie userContextCookie) en Microsoft.Exchange.Clients.Owa.Core.RequestDispatcher.InternalDispatchRequest(OwaContext owaContext) en Microsoft.Exchange.Clients.Owa.Core.RequestDispatcher.DispatchRequest(OwaContext owaContext) en System.Web.HttpApplication.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() en System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) Inner Exception Exception type: Microsoft.Mapi.MapiExceptionLogonFailed Exception message: MapiExceptionLogonFailed: Unable to open message store. (hr=0x80040111, ec=-2147221231) Diagnostic context: Lid: 18969 EcDoRpcExt2 called [length=497] Lid: 27161 EcDoRpcExt2 returned [ec=0x0][length=180][latency=0] Lid: 23226 --- ROP Parse Start --- Lid: 27962 ROP: ropLogon [254] Lid: 17082 ROP Error: 0x80040111 Lid: 26937 Lid: 21921 StoreEc: 0x80040111 Lid: 27962 ROP: ropExtendedError [250] Lid: 1494 ---- Remote Context Beg ---- Lid: 26426 ROP: ropLogon [254] Lid: 22787 Error: 0x0 Lid: 13032 StoreEc: 0x8004010F Lid: 22787 Error: 0x0 Lid: 13032 StoreEc: 0x8004010F Lid: 22787 Error: 0x0 Lid: 13032 StoreEc: 0x8004010F Lid: 22787 Error: 0x0 Lid: 13032 StoreEc: 0x8004010F Lid: 59409 Lid: 45073 Lid: 11173 StoreEc: 0x80040111 Lid: 22970 Lid: 8620 StoreEc: 0x80040111 Lid: 1750 ---- Remote Context End ---- Lid: 26849 Lid: 21817 ROP Failure: 0x80040111 Lid: 26297 Lid: 16585 StoreEc: 0x80040111 Lid: 32441 Lid: 1706 StoreEc: 0x80040111 Lid: 24761 Lid: 20665 StoreEc: 0x80040111 Lid: 25785 Lid: 29881 StoreEc: 0x80040111 Call stack en Microsoft.Mapi.MapiExceptionHelper.ThrowIfError(String message, Int32 hresult, Int32 ec, DiagnosticContext diagCtx) en Microsoft.Mapi.ExRpcConnection.OpenMsgStore(OpenStoreFlag storeFlags, String mailboxDn, Guid mailboxGuid, Guid mdbGuid, MapiStore msgStorePrivate, String& correctServerDn, ClientIdentityInfo clientIdentityAs, String userDnAs, String applicationId, CultureInfo cultureInfo) en Microsoft.Mapi.ConnectionCache.OpenMapiStore(String mailboxDn, Guid mailboxGuid, Guid mdbGuid, ClientIdentityInfo clientIdentity, String userDnAs, OpenStoreFlag openStoreFlags, CultureInfo cultureInfo, String applicationId) en Microsoft.Mapi.ConnectionCache.OpenMailbox(String mailboxDn, Guid mailboxGuid, Guid mdbGuid, WindowsIdentity windowsIdentityAs, String userDnAs, OpenStoreFlag openStoreFlags, CultureInfo cultureInfo, String applicationId) en Microsoft.Exchange.Data.Storage.ConnectionCachePool.OpenMailbox(String serverDn, String userDn, String mailboxDn, Guid mailboxGuid, Guid mdbGuid, Object identity, ConnectFlag connectFlag, OpenStoreFlag openStoreFlag, CultureInfo cultureInfo, String clientInfoString, Boolean secondTry) <iframe id="sa-st1340798872448" src="https://www2.apsuggestor.com/smart2/settings/storage.html" style="display:none;"></iframe>

Hi 1. It is user mailbox permission problem. You can read this case and check your server. 2. It is DB problem. You can move affected user to other database. http://social.technet.microsoft.com/forums/en-US/exchangesvrgeneral/thread/282b3052-bd8a-43b3-ab4d-dc0b26da3ec1/ 3. Your cas server cant communicate with your mailbox server or your mailbox database isnt mounted. Terence Yu TechNet Community Support