PST to MBOX Converter Tool for Windows 10, 11: Free Download

How to download and use PST to MBOX Converter Software

1

Open the PST or OST file

Point the PST to MBOX Converter tool at the .pst or .ost file. It is read straight off the disk. The folder tree appears in the left pane, and you can open any message before converting.

2

Tick the folders you actually need

Select folders in the tree. Empty ones can be skipped, Deleted Items left out, and the date range narrowed to the years that matter.

3

Choose MBOX and the output folder

Set the output format to MBOX on the Convert tab. If a mailbox file with that name already exists, choose what happens to it. Append tops up an archive you converted a month ago. Rename and overwrite are available too.

4

Take the result into your mail client

Hand the output directory to Thunderbird. Import it with the ImportExportTools NG add-on or drop it into the profile folder. Nothing needs renaming or reassembling.

Folder tree in .sbd layout

MBOX carries no hierarchy of its own. To keep Inbox / 2026 / Clients standing, PST to MBOX Converter Software writes each folder as a mailbox file and puts its children into a directory named after that file with an .sbd suffix. Thunderbird uses the same layout on disk. Most tools claim to preserve the hierarchy and leave you with a flat pile of files to import one by one.

Original internet headers, word for word

For mail that arrived over SMTP, the whole original header block is copied from the PST file verbatim. The Received chain, DKIM signatures, Return-Path and List headers come across as written. In a test archive of 18,600 real messages, every SMTP-delivered message had that block. Mail you sent yourself never has it, so those headers are rebuilt from the MAPI properties.

Real recipient addresses, not display names

To and Cc are assembled from the archive's recipient table, so the output carries actual SMTP addresses instead of a bare 'Ivan Petrov'. In the same archive, that worked for 99.6% of messages, and every recipient found there had an address. Display names look fine in a message list and fall apart when somebody hits Reply.

Read status through X-Mozilla-Status

The PST message flags for read, replied and flagged are written into X-Mozilla-Status as hex 0001, 0002 and 0004. Thunderbird reads those states from that header.

Attachments byte for byte

Attachments are written out unchanged. In our tests, every one matched the source by sha256. Inline images stay in the body because the cid: reference in the HTML still matches the Content-ID of the part. There is no re-encoding or 'attachment converted' stub.

Filters, streaming and a report

Use a date range, skip empty folders, exclude Deleted Items, export without attachments, or append into an existing mailbox. Writing is streamed rather than buffered, so a heavy Inbox does not need to fit in memory. In our tests, the archive above went through in 49 seconds with no failures, and a plain text report per folder is placed next to the result.

Who needs SoftOrbits PST to MBOX Converter

People leaving Microsoft 365

When the subscription lapses or the work laptop goes back, years of mail need a home that costs nothing to keep. Thunderbird is where most of it lands. The hard part is getting the mail out of the .pst.

Admins moving a team off Outlook

Dozens of archives, each with its own folder scheme and junk. Date filters and the Deleted Items switch cut the volume before conversion. A per-folder report says what went through and what did not.

Anyone holding an inherited archive

A .pst handed over by a colleague who left, and no Outlook on the machine to open it with. Open it, read what is in there. Then convert only the part that still matters.

Where the MBOX output opens

MBOX is a plain concatenation of messages, so one conversion serves several clients. The .sbd directories are a Thunderbird convention. Other clients ignore them and open the mailbox files directly.

Mail client	Platform	How it takes the output
Mozilla Thunderbird	Windows, macOS, Linux	Native on-disk format. Import the output directory with ImportExportTools NG, or copy it into the profile folder.
Apple Mail	macOS	File, Import Mailboxes, Files in mbox format. Imported mail arrives in an Import mailbox and is moved from there.
Postbox	Windows, macOS	Built on the Thunderbird codebase, so it reads the same mailbox files and the same .sbd directories.
Eudora and other legacy Windows clients	Windows	Eudora keeps mail in mbox-style .mbx files, so a mailbox is taken in once it is renamed and placed in Eudora's mail folder.
mutt and other Unix mail clients	Linux, BSD	Output is mboxrd, so a line starting with From in the body is escaped with a leading angle bracket and parsers do not split a message in the wrong place.

Download for Free

PST to MBOX Converter Software

Price

from $ 29.99

Version

1.8

File Size

4.5 Mb

Last updated on

11/08/26

System Requirements

Windows 11/10/8.1/8/7 (32/64 bit)
Intel i3, AMD Ryzen 5 or above
4 GB of RAM or above
NVIDIA® GeForce® series 8 and 8M, Intel® HD Graphics 2000, Quadro FX 4800, Quadro FX 5600, AMD Radeon™ R600, Mobility Radeon™ HD 4330, Mobility FirePro™ series, Radeon™ R5 M230 or higher graphics card with up-to-date drivers
1280 × 768 screen resolution, 32-bit color
1 GB of free hard disk space or above

Frequently Asked Questions

Can I convert a PST file to MBOX without Outlook installed?

Yes. The archive is read directly by the program, so Outlook does not have to be installed. No Exchange profile or mail account either. That is the usual case anyway. People convert PST to MBOX precisely when Outlook is already gone, after an expired subscription or on a machine that never had it.

Can Thunderbird open a PST file on its own?

No. Thunderbird has no PST reader. Its Outlook import menu works only when a configured Outlook installation on the same computer hands the mail over through MAPI. Convert the archive to MBOX first.

How do I get the converted mail into Thunderbird?

PST to MBOX Converter output uses Thunderbird's native on-disk layout: a mailbox file per folder plus a matching .sbd directory for its subfolders. Import it with the ImportExportTools NG add-on, whose import list covers mbox files together with their structure, or copy the same directory into the Thunderbird profile folder.

Will my Outlook folder tree survive the conversion?

Yes. And it is the one thing worth verifying yourself in any converter. Open the output directory afterwards. Every folder should have its own mailbox file with a matching .sbd directory beside it, and the subfolders should sit inside that directory rather than flattened out into names like Inbox_2026_Clients. That is the shape Thunderbird keeps a nested tree in on disk.

Can messages go missing during conversion?

They should not, and you do not have to take that on faith. Message loss is a real complaint in mail migrations. People compare counts before and after an export and find items missing, usually long after the source archive has been deleted. So every folder is counted here and the counts go into plain text report next to the result. Compare source and output folder by folder instead of trusting a progress bar.

Are read, replied and flagged marks preserved?

In Thunderbird, yes. The state rides in the X-Mozilla-Status header, which Thunderbird picks up on import. Other mail clients treat that header their own way and most simply ignore it, so the same mailbox can show up as all unread there.

Is there a free way to convert PST to MBOX?

If Outlook and Thunderbird are both installed and working on the same PC, Thunderbird can import from Outlook directly. Open source readers pull messages out of a PST file on the command line. Those routes leave you without the tree in Thunderbird's layout, and they have no date filter to keep the batch small.

Which mail clients can open the MBOX files it writes?

Thunderbird first of all. Postbox shares its codebase, so it reads the same files. Apple Mail imports them on macOS, and on Linux mutt reads them as they are while Claws Mail imports them. The files are mboxrd, so a From line inside a message body is escaped and no parser splits the mailbox in the wrong place.

How do I export my mail from Outlook to a PST file first?

In classic Outlook, use File > Open and Export > Import/Export > Export to a file > Outlook Data File (.pst). Pick the top of the mailbox and tick Include subfolders so the whole tree goes in. If your mail sits in an .ost cache, there is nothing to export because .ost files open here directly.

Can it convert several PST files in one run, or repair a damaged or password-protected archive?

One archive per session for now. A queue of several files is planned but not in this version. A corrupted PST returns an error instead of a half-converted mailbox. A PST locked with a password is handled by our separate Outlook PST Password Recovery product.

Download PST to MBOX Converter Software for Windows