I have SBS 2003 with Exchange Server running. Have had no problems until today. One user reported problem message "Cannot start Microsoft Outlook. Unable to open the Outlook window. The set of folders could not be opened." Soon found that no user could open Outlook. Users which had it open could not save changes to contacts or send anything. I stopped and restarted all Exchange services on the server. Not a fix. I rebooted the server. All users still get the same error except on user with Outlook 2007. That user can open Outlook but is not connected, or offline. The user "Administrator" can open Outlook but has message "Unable to display folder". When I try to connect using Outlook Web Access I get to the login screen okay. After entering user name and password I get the message "HTTP/1.1 503 Service Unavailable" I tried running the command "netsh int ip set chimney DISABLED" on the server but it did not help. I have checked several times to see if the mailbox store is mounted. An hour after the problem started it was, but now it has been dismounted a couple times I checked. I have remounted it but it has not helped. when mounted sometimes I am able to see more information, and sometimes it appears empty. Email is coming into the system because most of the spam is redirected to system directories and it is getting out there. But right now nothing in Outlook, including Tasks, Calendar, Contacts and Email is available.