Does your workplace still allow .pst files to be handled by employees? They shouldn’t. We all know the “need” people have for keeping old emails (and files for that matter, but that’s a different story – and another blogpost!).
First off, “.pst” files are Outlook data files that where used to store content(mail and other Outlook stuff) locally on a computer. These files were originally created to help users store email outside the mailbox. Back then, storing emails locally made sense because mailbox sizes where quite small. Today they solve a problem that doesn’t really exist any more.
Today, mailboxes are larger, but users also store much more data. If the organization does not enforce archiving policies after a certain time, users may keep years of old mail in manually created PST files.
“Can’t we just let users import them into Outlook?” Technically yes, but don’t let them.
PST files live outside of Purview governance, a .pst file on a user’s disk (or Onedrive to some extent) is not indexed and classified. This means no retention policies, no litigation hold, no eDiscovery searches can find it, no DLP policies can inspect the content.
On the more malicious side of things, a user can also move pst files to USB, upload them to a personal cloud account and steal the data.
So, what we are really doing by blocking user export and import of .pst files is moving towards better governance of data.
IT admins can then use Microsoft Purview to upload PST content into Exchange Online. The messages become part of the mailbox or online archive, which makes them searchable by Copilot. And voilà, we have moved from a standalone file to governed mailbox data.
The how-to do this is described here. I have used the network upload myself. I can’t say it’s my favorite Preview feature, but it works once you get in the flow of it.
PST files had their time, but that time has passed. In a modern Microsoft 365 environment, important data should be searchable, protected, retained, and governed — not hidden away in loose files on endpoints or personal storage.
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