Well I have saw only a few posts relating to this event id but none are exactly like this issue so I am posting a new thread. First some background information. We have an Exchange 2007 server running Mailbox, Client Access, and Hub Transport role as this is just currently a single server setup. We also have two staff (myself included) that access Exchange via Windows Mobile device and a Blackberry Enterprise Server installed on the same machine for one staff accessing Exchange via his Blackberry. Everyone once in a while (read: every couple of weeks) we have to reset the Exchange server because we lose all access to Exchange (Outlook, OWA, ActiveSync). I finally was able to pinpoint the errors and starting around 3:00 a.m. I get a series of errors below that go away once the server resets and they all point to ActiveSync. Below are the errors:Event ID: 1022Source: MSExchange ActiveSyncDescription: The connection between the Client Access server and Mailbox server "<server_name>" failed. Event ID: 1016Source: MSExchange ActiveSyncDescription: Exchange ActiveSync has encountered repeated failures when it tries to access data on Mailbox server <server_name>. Exchange ActiveSync will temporarily stop making Exchange ActiveSync requests to the Mailbox server. The process will be postponed for [60] seconds. Then after those two errors show up for the two accounts that have Windows Mobile access to the Exchange server then the Application log shows this the rest of the way:Event ID: 4001Source: MSExchange System Attendant MailboxDescription: A transient failure has occurred. The problem may resolve itself in a while. The service will retry in 56 seconds. Diagnostic information: Cannot open mailbox /o=<domain>/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Configuration/cn=Servers/cn=<server_name>/cn=Microsoft System Attendant.Microsoft.Exchange.Data.Storage.ConnectionFailedTransientException: Cannot open mailbox /o=<server_name>/ou=Exchange Administrative Group So thats the story. Anyone have this problem before?Thanks,Troy

Hi Troy, From the event log, we can see all three items indicate mailbox cant be accessed. As your CAS and mailbox installed on the same server, so there is no server connection issue, the issue can be caused by Microsoft Exchange Information Store service had been stopped. You can manually restart it rather than restart server if you need. In most cases, its caused by the third party application. Please disable all third party software(including BlackBerry) and test the issue again. Nevertheless, if the issue persists, please use BPA to do a health check to see if there is any problems. A KB article in Exchange 2003 environment for your reference. The Microsoft Exchange Information Store service may stop responding randomly, or the service may crash, in Exchange Server 2003 http://support.microsoft.com/kb/952772 Thanks, Elvis