A PST file is a so-called Personal Storage Table, ie a storage for personal data. PST is a proprietary but open format used by Microsoft Outlook and Microsoft Exchange to manage contact information. Microsoft Outlook is a contact manager and part of Microsoft Office. Pst files are data containers that contain, among other things, emails, addresses, calendar data and tasks.
In addition to a standard PST file, Outlook can also manage multiple PST files. Since there are always problems with corrupt PST files, it is recommended to create backups regularly, taking into account that, among other things, account and program settings are not saved in the PST file. To repair defective PST files, the program scanpst is installed with Outlook.
The maximum file size of a PST file can now (from Outlook 2003) be up to 20 GB, before that it was only 2 GB. Very large PST files can cause Outlook to slow down noticeably. Defragmenting the hard disk or archiving old emails can help here.
The free Outlook Express does not use PST files but can import them. Since the PST format is open, other mail programs can also import PST files, for example Thunderbird. Since the PST format has meanwhile been changed several times, problems can occur during import. Unfortunately, most programs rely on Outlook being installed to import a .pst file.