Networked .pst files are also unsupported.
PST=BAD #1: They're fragile, especially as they get big. They get corrupted easily.
PST=BAD #2: Outlook limits the size of PST files to 2GB. Once past this limit, Outlook can no longer open the file, and the data is inaccessible.
PST=BAD #3: You have to run the Inbox Repair Tool on them way too often.
PST=BAD #4: Your users don't back them up if on their own PCs.
PST=BAD #5: Your users don't compact them. They just get bigger and bigger.
PST=BAD #6: Your users forget their PST passwords. Even though there are unsupported tools to crack them, it can take a significant amount of time to do so.
PST=BAD #7: You lose single instance store (SIS).
PST=BAD #8: Messages take up more space in a PST than in an Exchange store.
PST=BAD #9: It's simply nuts to store PSTs on a network drive. They just end up taking up more space.
PST=BAD #10: A PST can be opened by only one machine at a time. This means a manager and assistant can't work from the same PST simultaneously, and precludes team access.
PST=BAD #11: You cannot clean up PST files after virus infestations!
PST=BAD #12: Future applications, such as unified messaging, will be poorly implemented when using PSTs. Groupware applications that work with the mailbox probably won't work at all.
PST=BAD #13: You cannot use Outlook Web Access to read your downloaded messages.
PST=BAD #14: One might think that it will be easier to restore a single mailbox by using server-based PSTs. However, with proper implementation of the Ed Crowley Never Lose a Mailbox Procedure, it should never ever be necessary to restore a mailbox.
PST=BAD #15: PST files are not secure. Anyone with access to the PST file can open it using the right tools.
PST=BAD #16: For road warriors, OSTs are a much superior storage technique, especially with the improvements made with Outlook 98. They allow untethered computing at a higher level than with PSTs, plus with the added security of a backed-up information store on the server.
Pat Richard, MCSE(2) MCSA:Messaging, CNA(2)