I have an SBS 2003 Server that at some point over the weekend, every weekend, loses email functionality. Specifically, the information store (IS) isn't accessible. If I attempt to cycle the IS service, it hangs in "stopping" mode. All other services on the server are fully functional (file, print, vpn...). The event log yields no clues as to what is happening.
I have re-applied SP2 for Exchange 2003. I have also done an offline integrity check and defrag of the IS.
A reboot resolves the issue until next weekend.