What is a .pst File?

When e-mail messages are collected for review in litigation, they are often delivered to attorneys or their e-discovery vendors in .pst files.  These “personal storage tables” or “personal folder files” are Microsoft Outlook data files containing individual Outlook items such as email messages, calendar items and contacts.  .pst files serve a couple purposes including saving disk space and file portability. Individual mailboxes are often subject to space quotas and messages, calendar items and the like may be moved from individual mailboxes into .pst files to free up space. Another use of .pst files is to archive or export information from Outlook. It is this latter use of .pst files utilized in electronic discovery. A .pst file of emails is created which is then imported into e-discovery software so the individual messages may be reviewed for use in the case (or not).