As a Microsoft program manager recently quipped, Outlook users tend to be either "pilers" or "filers." Whether they have an Inbox with 20,000 items or 100-plus folders, though, Outlook users have all grown steadily more dependent on the data in their folder sets and want that data to be available wherever they happen to be working. Because at least half of all Outlook users never connect to an Exchange Server system and because many Exchange users also store data outside their server mailboxes, backup and synchronization can frequently be a challenge.

The personal folder store (PST) is an ingenious invention that offers standalone users the opportunity to use all of Outlook's core features. It's definitely personal, though, with some built-in constraints that have become more restricting as the Outlook user community has matured:

* When Outlook (or another messaging application) is using a PST, another program can't change, read, or even copy it. * Outlook assumes that the user who's reading information in a PST will also want to change or add information. Therefore, you can open a PST only from a writable location; Outlook can't work with read-only disks (e.g., archived CD-ROMs). * The total size of a PST can't exceed 2GB.

End users ran up against these limitations as soon as Outlook was bundled with Microsoft Office 97. Because PST files couldn't be copied while in use, LAN administrators found it difficult to implement backup strategies for data, and the PST file's structure made coordinating information kept at work and home difficult for individuals. Even the most obsessive Outlook housekeeper found 1.44MB disks (the most common external medium at that time) woefully inadequate for storage or transfer.

Since then, various workarounds for PSTs' deficiencies have been tried. The Personal Folders Backup (Pfbackup) add-in for Outlook 2002 and Outlook 2000, which can automatically copy files when the user exits Outlook, partially solved the backup dilemma. The add-in, combined with increased disk capacity and popular CD-RW drives, has rendered backup less worrisome today.

Synchronization between machines has been a harder nut to crack. After a promising beginning, most Web-based storage and synchronization services have disappeared from the scene, although a few subscriber services remain. Some customers have resorted to using their PDAs as transfer points to keep their work and home machines synchronized. Others use Pfbackup to make regular copies of their entire folder sets on a portable medium to shuttle between two machines. Fortunately for the pilers among us, recent advances in storage technology have delivered a variety of low-cost options for transferring growing amounts of data. USB keychain devices, microdrives, and CompactFlash and Secure Digital (SD) cards can accommodate hefty archives of as much as 1GB without the connection and driver complications of earlier storage solutions. Users who are pushing up against the PST 2GB maximum can slip a cast-off 2.25-inch laptop drive into an economical USB 2 case and keep piling on the data when they convert to the new expanded Unicode store available in Outlook 2003 (formerly code-named Outlook 11).

Even as the backup and synchronization workarounds have evolved to use new technologies, the fundamental problem remains: As innovative as it might once have seemed, the basic storage system for non-Exchange users is less than equal to the needs of those users today. And the constraints that inhibit productive use of one's personal data are the same as those that prevent concurrent sharing of that data with other users--the number-one requirement of Outlook users in small businesses. Outlook 2003 will include a new model for working with user data in an Exchange environment; let's hope that the next Outlook version will bring comparable changes for the other half of the Outlook user community.