Hi, We are having Exchange 2007 setup with one Single Copy Clustered Mailbox Server with two node, two CAS and two Hub Transport Servers. To support the additional users we have planned to install another set of Mailbox servers in CCR since our Exchange 2010 implementation is going to take some more time. We have installed Exchange 2007 SP3 RU6 on HUB & CAS Servers and installed two new Servers with Windows 2008 R2 and Exchange 2007 SP3 RU6 in CCR in virtual environment. Only old Mailbox Servers were left without upgrading to SP3 RU6 since we were running short of time. Post implementation of new servers we have moved 30% of users from ols Mailbox Server to new Mailbox Server and found working fine. Since last1-2 days we are facing issue with users mailbox OWA access who are having mailbox on Old Mailbox Server. Below is the error when user try to access the mailbox through OWA, however users in new Mailbox Servers are working fine. Exception Exception type: Microsoft.Exchange.Data.Storage.NoMoreConnectionsException Exception message: Cannot open mailbox /o=Orgname/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=testing. Call stack 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) 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) 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) Microsoft.Exchange.Data.Storage.MailboxSession.Initialize(LogonType logonType, ExchangePrincipal owner, DelegateLogonUser delegateUser, Object identity, OpenMailboxSessionFlags flags) Microsoft.Exchange.Data.Storage.MailboxSession.CreateMailboxSession(LogonType logonType, ExchangePrincipal owner, DelegateLogonUser delegateUser, Object identity, OpenMailboxSessionFlags flags, CultureInfo cultureInfo, String clientInfoString) Microsoft.Exchange.Data.Storage.MailboxSession.Open(ExchangePrincipal mailboxOwner, WindowsPrincipal authenticatedUser, CultureInfo cultureInfo, String clientInfoString) Microsoft.Exchange.Clients.Owa.Core.OwaWindowsIdentity.CreateMailboxSession(ExchangePrincipal exchangePrincipal, CultureInfo cultureInfo) Microsoft.Exchange.Clients.Owa.Core.UserContext.Load(OwaContext owaContext) Microsoft.Exchange.Clients.Owa.Core.RequestDispatcher.CreateUserContext(OwaContext owaContext, UserContextKey userContextKey, UserContext& userContext) Microsoft.Exchange.Clients.Owa.Core.RequestDispatcher.PrepareRequestWithoutSession(OwaContext owaContext, UserContextCookie userContextCookie) Microsoft.Exchange.Clients.Owa.Core.RequestDispatcher.InternalDispatchRequest(OwaContext owaContext) Microsoft.Exchange.Clients.Owa.Core.RequestDispatcher.DispatchRequest(OwaContext owaContext) System.Web.HttpApplication.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) Inner Exception Exception type: Microsoft.Mapi.MapiExceptionNoMoreConnections Exception message: MapiExceptionNoMoreConnections: There are no available connections in the connection cache Call stack Microsoft.Mapi.ConnectionCache.OpenMapiStore(String mailboxDn, Guid mailboxGuid, Guid mdbGuid, ClientIdentityInfo clientIdentity, String userDnAs, OpenStoreFlag openStoreFlags, CultureInfo cultureInfo, String applicationId) Microsoft.Mapi.ConnectionCache.OpenMailbox(String mailboxDn, Guid mailboxGuid, Guid mdbGuid, WindowsIdentity windowsIdentityAs, String userDnAs, OpenStoreFlag openStoreFlags, CultureInfo cultureInfo, String applicationId) 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) We have stopped AV and ensured that no backup is running, but there is no improvement. Could any one suggest to fix the issue... Pls help... Regards:Mahesh

Hi 1. It is user permission problem You can run cmdlst to modify it Get-MailboxPermission tgallagher | where { ( $_.Isinherited -like "False" ) -and ( $_.Deny -like "true" ) } | ForEach {Remove-MailboxPermission $_.Identity -user $_.user -AccessRights FullAccess -Deny:$true} 2. CAS problem netsh int tcp set global chimney=disabled netsh int tcp set global rss=disabled Increase the ConnectionCacheSize to 250. Note : Take a backup copy of Web.config file before doing any changes. Open "web.config" file with Notepad on CAS Server . The file is located following directory as default, <Drive letter>:\Program Files\Microsoft\Exchange Server\ClientAccess\Owa Locate the following line under the "appSettings." <add key="ConnectionCacheSize" value="100"> Change the value from 100 to 500 Run IISReset TechNet Subscriber Support in forum If you have any feedback on our support, please contact tngfb@microsoft.comTerence Yu TechNet Community Support

Hi Do you have anything update on your issue ?Terence Yu TechNet Community Support

Hi Issue didnt reoccure post restart of IIS in both CAS servers, we kept this under observation. Thanks for your revert.Regards:Mahesh