When Outlook is configured to save email to a .PST (personal folders) file on the local machine, this takes the
burden of message storage off the server. However, this means that each user's email is stored locally, and may be susceptible to damage.
One of the most common forms of damage is when a .PST file exceeds 2 GB in size. This may not sound like damage at first, but Outlook has problems dealing with files of that size or larger (although this limitation is to be corrected shortly). If a user has been retaining a great deal of email without performing any archiving, or if the archives themselves are beginning to approach or exceed 2 GB, there may be a risk of data loss.
There are several ways to avoid this problem. One is to store all mail in the Exchange store rather than on the clients in PST files, but some organizations prefer using distributed rather than central storage simply because it is less of a burden on the central server.
A second preventative option is to keep up to date on recent hotfixes Office XP Service Pack insures that once a PST file reaches 1.82 GB, the user will not be able to add new mail to the store until the condition is corrected. Office 2000 Service Release 1 and 1a also update Outlook 2000 so that more data cannot be added when the store reaches 2 GB, but it doesn't warn the user. (Another preventative strategy is to keep the PST file on an NTFS partition rather than FAT (if possible) to keep data corruption to a minimum. This could either be a local file or a file on a shared server.)
Damaged or corrupt PST files can be repaired with the SCANPST.EXE command-line tool, which is generally installed with Outlook. When run against a PST file, it creates a backup copy of the file on demand (which is highly recommended) and then attempts to correct the errors. SCANPST.EXE also works on .OST files used for offline access to Exchange Server folders. If an .OST file is damaged to the point where SCANPST.EXE cannot fix it, change the settings for the Exchange Server service on the server to refer to a new .OST file and then synchronize it with the server.
If a file has grown beyond the 2 GB limit, there is a Microsoft Tool named PST2GB, which can truncate files to make them readable again. The one big drawback to this tool is that anywhere from 25-50 MB may be truncated from the end of the file and will not be recoverable. Further information on this tool can be found at support.microsoft.com/?kbid=296088.
In every case, repair operations should always be done on backups, not original copies of .PST and .OST files.
Serdar Yegulalp is the editor of the Windows 2000 Power Users Newsletter. Check out his Windows 2000 blog for his latest advice and musings on the world of Windows network administrators – please share your thoughts as well!