I recently came across an article in the Microsoft Database titled "Personal folder files are unsupported over a LAN or over a WAN link" (KB 297019). Upon further exploration of this topic, I discovered the OutlookPower article "How to share your .PST files" by David Gewirtz, which concludes "So, in summary, the answer to how to share your .PST files is...don't."

My experience is very different, and I'd like to share what I see as the "positive side" of .PST sharing. Our situation is as follows -- we are an academic institution that uses Microsoft Exchange Server to provide email service for at least 10,000 clients (I don't know the true size of the system, but this is a conservative lower limit). Our Exchange mailboxes are limited to 20MB in size, though we can sometimes get them "enlarged" to 40MB. We also are all members of an enterprise-wide "domain", and authenticate to central domain controllers.

Needless to say, even a 40MB mailbox can fill up quickly, particularly for those of us involved in manuscript or grant preparation, or in academic publishing (such as being on the editorial board of a journal). Our Exchange team recommends Public Folders (.PST files) for this purpose to provide a place to keep the "overflow" from our mailboxes (and to keep the "old" e-mails which often contain information we need to retrieve at a later date). Note that, in this model, .PST files are not being used as the prime recipient of incoming email messages (they remain on the Exchange server), but are used as "storage locations" for old email. The only time data gets added to these folders are when the user deliberately moves data from Exchange to the .PST.

I am well aware of the 2GB limitation of .PST files, and have cautioned users about monitoring the file size -- a practical solution is to name the files "Old Mail 1998-2002", "Old Mail 2035-2005", etc. A bigger problem is that the default location for the .PST file is in a hidden file within the user's local profile -- being hidden, it is harder to "mount" as a Personal Folder (something one had to do "by hand" in Outlook 2000) to allow retrieval of information from the folder, and being local on the hard drive, there is no obvious backup mechanism to protect the integrity of these folders.