In Microsoft Exchange Server 2019 or Exchange Server 2016, assume that you have several database availability groups (DAGs) that have multiple mailbox databases. You could experience an issue that the store worker process crashes randomly for different mailboxes on different databases. Additionally, the following event is recorded in the application event log:
Time: TimeID: 1002Level: ErrorSource: MSExchangeISMachine: ComputerNameMessage: Unhandled exception (System.NullReferenceException: Object reference not set to an instance of an object.at Microsoft.Exchange.Server.Storage.StoreCommonServices.AddressBookEID.IsAddressBookEntryId(Context context, Byte entryId, Eidt& eidt, String& emailAddr)at Microsoft.Exchange.Server.Storage.StoreCommonServices.AddressInfoGetter.GetAddressType(Context context, ISimpleReadOnlyPropertyBag bag, AddressInfoType ait)…
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
To fix this issue, install one of the following updates:For Exchange Server 2019, install the Cumulative Update 1 for Exchange Server 2019 or a later cumulative update for Exchange Server 2019.