Glossary
What Is a PST File?
A PST file is Outlook's Personal Storage Table, a single database file that keeps your emails, contacts, calendar entries, and tasks on your own computer. Outlook creates it to store a mailbox locally, separate from any mail server. A modern PST can grow to as much as 50 GB, which is why large mailboxes are usually split or archived.
TL;DRPST is Outlook's local mailbox file. Convert it to PDF to open and read the messages without Outlook.
50 GB
the maximum size a modern Unicode PST file can reach in Outlook 2010 and later
What a PST File Stores
A PST is not just mail. Outlook packs the whole personal mailbox into one file:
- Email messages, with their folders and read or unread state.
- Contacts, calendar appointments, tasks, and notes. Appointments pulled out of a PST leave as .ics files, so a calendar export to a spreadsheet is one step from there. Contacts saved one by one leave as .vcf cards, and a Microsoft Store app can turn VCF contacts into a CSV file.
- Rules, signatures, and other account settings tied to the data file.
Because everything lives in one place, copying a single PST moves a person's entire Outlook history to a new machine. If the mail still sits on a server, a
mailbox migration tool for IMAP accounts copies it straight into the new account instead. Old .pst files left on past laptops can end up in one place too: a tool to
combine PST files writes them into a single new data file.
Why PST Files Grow and Break
The single-file design is also the weakness. Older ANSI PST files from Outlook 2002 and earlier were capped near 2 GB and would corrupt once they hit that wall. Unicode PST files lifted the limit, but a file that swells past tens of gigabytes still slows Outlook and risks damage if the program closes mid-write. Attachments usually carry most of that weight, and an
email attachment remover for PST files saves a copy of the mailbox without them.
Never copy a PST while Outlook is open. The file is locked and a half-written copy can come back corrupt. Close Outlook first, then move the file.
How to Open a PST Without Outlook
You do not always have Outlook on the PC holding the file. To read what is inside, a way to
open a PST file without Outlook shows the folder tree and the messages as they are. When you need the mail outside the container, a converter reads the PST directly and turns the messages into PDF documents you can open and search anywhere. A folder of saved web pages is a simpler version of the same problem, one file plus a resources folder instead of a whole mailbox, and
Batch HTML to PDF Converter turns the whole folder into PDF the same way.
An export outlook to thunderbird move is a different job than reading a copy: it converts the same PST into MBOX, the folder-per-file format Thunderbird stores mail in natively, instead of a PDF you view outside any mail client.
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