LetterlarkHow to open a PST file without Outlook
A .pst file is Outlook's mailbox archive. Microsoft doesn't offer a free stand-alone PST viewer, but you don't need Outlook to read one. Here are the options, from quickest to most technical.
Updated 2026-10-26 · 6 min read
1. Open it in your browser (any computer)
- Open Letterlark in Chrome, Edge, Firefox or Safari.
- Drop the .pst file on the page. Large files are read piece by piece from disk, so multi-gigabyte archives open – indexing takes a while.
- Browse the folder tree, search subject, sender, recipients, body text and attachment names, and download attachments.
Nothing is uploaded: the page's security policy blocks network connections. This also works for .ost files.
2. readpst (free, command line)
The open-source libpst project includes readpst, which converts a PST into MBOX or EML files. Install it with brew install libpst on macOS or sudo apt install pst-utils on Debian/Ubuntu, then run readpst -o out/ archive.pst. You then need a mail program or MBOX viewer to read the output.
3. Outlook for Mac or a new Outlook profile
If you have a Microsoft 365 licence on any computer, Outlook can import or open the PST (Windows: File › Open & Export › Open Outlook Data File; Mac: File › Import). That counts as “with Outlook”, but it may be on a different machine than the one you're using.
4. Why Thunderbird usually doesn't work
Thunderbird's Outlook import on Windows reads the mail through Outlook's own components, so it generally needs Outlook installed and set up. On Mac and Linux it can't read PST files directly. Convert the PST to MBOX first (PST to MBOX) and Thunderbird can use it.
Search an old PST for one email
If you only need to find a message in an old archive (for a dispute, tax question or a lost attachment), a viewer is fastest: open, type the search term, filter by date or “has attachments”, and save that one message as PDF or EML.
Limits to know
- Damaged PST files may not open – Letterlark is a viewer, not a repair tool. Microsoft's Inbox Repair Tool (scanpst.exe) comes with Outlook for Windows.
- PST “passwords” are not real encryption; strongly encrypted PSTs and S/MIME-encrypted messages can't be read.
- Contacts, calendar items and tasks show as basic text only.
Open your mail file now. Letterlark opens PST, OST, MSG, EML and MBOX files in Chrome, Edge, Firefox or Safari on Windows, Mac, Linux or Chromebook. Files are read on your computer – the app page cannot upload anything. Viewing and search are free without limit; exports (PDF, EML, MBOX, CSV, attachments) are free up to 20 messages at a time. A one-time license is $19 (Personal) or $49 (Pro, business use).
Questions and answers
Is there a free PST viewer from Microsoft?
No stand-alone one. Microsoft's route is to open the file in Outlook.
Can I open a PST file on a Chromebook or iPad?
On a Chromebook, yes – in the browser. On iPad, desktop-class browser features vary; small files usually work, large archives are better on a computer.
Can I open a PST file online?
Many “online” viewers upload your mailbox to their server. Letterlark runs in the browser but processes the file locally.
Sources and product names: libpst/readpst documentation; Microsoft Outlook help on opening Outlook Data Files (.pst); Mozilla Thunderbird import documentation. Microsoft, Outlook, Gmail, Google Takeout, Apple Mail and Thunderbird are trademarks of their owners. Letterlark is independent and not affiliated with them.