An Outlook PST, or Personal Storage Table file, is a Microsoft Outlook archive that stores email messages, folders, attachments, and sometimes calendar or contact data in one portable file. Users often keep PSTs to preserve older mail outside the main mailbox, which can make them easy to copy, move, and back up.
In cyber security, PST files matter because they can contain years of business conversations, sensitive documents, internal names, and even clues about passwords or account recovery. Attackers often look for PSTs during data theft because one file can expose a lot of context for phishing, impersonation, or extortion. Defenders reduce this risk by restricting where PSTs are stored, encrypting archives, limiting access, and reviewing retention so sensitive mail is not left in unmanaged files.