We recently added a front-end Exchange Server 2003 machine to our configuration. Since then, the machine's event log shows one event ID 9175 each minute, telling us that the mailbox stores are dismounted. We already know that! How can we shut off these continual annoying events?
This behavior is 100 percent by design. The System Attendant service is using the 9175 event to warn you that it can't accept or route email because it can't log on to the mailbox store. Whenever the System Attendant is running, it's going to try to log on to the system mailbox, and there's no direct way to suppress this event.
What you might be able to do is disable the System Attendant on your front-end server. If you use that server only for Internet client protocols (i.e., IMAP, Outlook Web Access—OWA, and POP), you can safely stop the System Attendant and set its restart state to Disabled. Doing so will halt the events. However, if you're using SMTP or if the front-end server offers Remote Procedure Call over HTTP Secure (RPC over HTTPS) services, you must leave the System Attendant running. SMTP requires the service for message acceptance and routing, and the System Attendant is in charge of updating the list of valid ports for RPC traffic for RPC over HTTPS. In this situation, you'll just have to get used to ignoring those events.