Can’t Access Public Folders from Outlook Web Access 2003 – 503 Service Unavailable Errors?
From Outlook Web Access, our Public Folders began showing 503 Service Unavailable errors unexpectedly. Public Folders were working fine from Outlook MAPI connections, but not from any IIS Exchange\Public virtual dependent services. The end cause ended up being a Front-end server in one of our sister campuses (domains) that had installed a new Exchange server and did not remove the Public Folder service and database. In fact, they dismounted the PF virtual which complicated the matter further. Read this article, which explains considerations of a Front-end\Back-end Topology.
"A public folder store should never be mounted, or present (even in a dismounted state) on the front-end server."
Rebooting the Public Folder or Front-end servers did not resolve the issue. When Exchange 2003 servers are restarted and Exchange services become online (System Attendant specifically), Exchange reads information out of Active Directory and the Configuration Container. When Exchange started on our servers they saw the new Public Folder server and began sending all Public Folder proxy requests to the offlined server. From ADSIEDIT (Support Tools), view your Configuration information regarding your Public Folder Hierarchy. Select Public Folders and select Properties. Select the attribute called msExchOwningPFTreeBL and select edit. The first server in our list was the Front-end Exchange server with the dismounted PF store. Our first fix was to remove the offlined server from this list and remove the PF store from the Front-end server. You must reboot your OWA servers to remove the AD information from cache.
One note of warning , if you have installed Service Pack 2 for Exchange 2003 on a Front-end server with a Public Folder database still present, it is nearly impossible to remove it. The best course of action is to delete it manually from the Configuration container via ADSIEDIT.