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Mbox Viewer

Guide

How to Convert Outlook PST/OLM to MBOX (Mac & Windows)

Outlook stores mail in PST (Windows) or OLM (Mac), which Mbox Viewer can't open directly. Here's how to convert PST and OLM files to standard mbox — free, step by step — then read them.

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Microsoft Outlook doesn’t use mbox. On Windows it stores everything in a PST database; Outlook for Mac uses an OLM archive. Neither is mbox, so Mbox Viewer can’t open them directly — you convert to standard mbox first, then open the result. This guide covers a free, reliable route for both formats and works on Mac and Windows.

Why convert at all?

PST and OLM are proprietary, single-vendor containers. Converting to the open mbox format frees your mail from Outlook, gives you one portable archive, and lets you read, search and export it in Mbox Viewer without an Outlook licence or a running mail account.

Convert a PST file (Outlook for Windows)

The cleanest free method uses Mozilla Thunderbird as a bridge — no paid converter required:

  1. Install Thunderbird and the free ImportExportTools NG add-on.
  2. In Outlook, make sure the mail you want is in a .pst (in Outlook: File → Open & Export → Import/Export → Export to a file → Outlook Data File (.pst)).
  3. In Thunderbird, install the ImportExportTools NG add-on, then use its tools (or the Thunderbird import wizard) to bring the PST data into a Local Folder.
  4. Right-click the folder → ImportExportTools NG → Export folder to write a standard .mbox file.

Prefer a one-step tool? Dedicated PST-to-MBOX converters exist for Windows; pick a reputable one, and always work on a copy of your PST.

Convert an OLM file (Outlook for Mac)

OLM is Mac-only and a bit more involved:

  1. In Outlook for Mac, export with Tools → Export… to create the .olm (work on a copy).
  2. Use an OLM-to-MBOX converter, or re-import the OLM into a mail client that can then export mbox (Thunderbird with ImportExportTools NG, as above).
  3. The output is one or more .mbox files.

Open the result in Mbox Viewer

Once you have a .mbox file (or an extension-less mbox), open it with Mbox Viewer:

  • Mac: double-click, drag & drop, or File → Open.
  • Windows: double-click in File Explorer, drag onto the window, or File → Open. (Mbox Viewer for Windows is available on the Microsoft Store.)

You get instant browsing, full search syntax, threaded conversations, attachment previews and export to EML, CSV or plain text — even for multi-gigabyte mailboxes, thanks to the streaming parser. Everything is local and read-only: your converted archive is never modified.

Open your archive with Mbox Viewer

Native Mac and Windows app. Streams MBOX and EML files of any size, fully offline.

Mac App Store Microsoft Store