When using exchange 2007, owa may not able to access the legency mailbox.

Solution: Just convert the legency mailbox to user mailbox.

Run the following command from the exchange command shell:

set-mailbox -applymandatoryproperties

Replace with the mailbox alias you like to convert.

Error Message:
Exception message: There was a problem accessing Active Directory.

Call stack

Microsoft.Exchange.Data.Storage.ExchangePrincipal.Save()
Microsoft.Exchange.Clients.Owa.Core.RequestDispatcher.DispatchLanguagePostLocally(OwaContext owaContext, OwaIdentity logonIdentity, CultureInfo culture, String timeZoneKeyName, Boolean isOptimized)
Microsoft.Exchange.Clients.Owa.Core.RequestDispatcher.DispatchLanguagePostRequest(OwaContext owaContext)
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.Exchange.Data.Directory.ADOperationException
Exception message: Active Directory operation failed on et3kdc01.FKNC.local. This error is not retriable. Additional information: Insufficient access rights to perform the operation. Active directory response: 00002098: SecErr: DSID-03150A45, problem 4003 (INSUFF_ACCESS_RIGHTS), data 0

Call stack

Microsoft.Exchange.Data.Directory.ADSession.AnalyzeDirectoryError(PooledLdapConnection connection, DirectoryRequest request, DirectoryException de, Int32& retries, Int32 maxRetries)
Microsoft.Exchange.Data.Directory.ADSession.ExecuteModificationRequest(ADRawEntry entry, DirectoryRequest request, ADObjectId originalId)
Microsoft.Exchange.Data.Directory.ADSession.Save(ADObject instanceToSave, IEnumerable`1 properties)
Microsoft.Exchange.Data.Storage.ExchangePrincipal.Save()

Inner Exception
Exception type: System.DirectoryServices.Protocols.DirectoryOperationException
Exception message: The user has insufficient access rights.