Corbett

OST to MBOX Converter

Corbett OST to MBOX Converter opens Outlook OST files on Windows and saves every folder as an MBOX file, in bulk or for chosen folders only. Folders, attachments and dates stay intact, and Outlook does not need to be installed. Try free demo first.

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4.6 out of 5 from 683 reviews

Works offline on your PC. Corbett never sees your OST files or messages.

Free demo, scanned clean on VirusTotal and a 30-day money-back window.

Lifetime licence from $99 Demo converts 10 emails per folder

Quick answer

What Is a OST to MBOX Converter?

An OST to MBOX converter opens Outlook OST files and saves every folder as an MBOX file. Corbett OST to MBOX Converter does that offline on Windows, so your mail opens in Thunderbird, Apple Mail and any client that imports MBOX.

What it opens

Offline OST files, Orphaned OST files, Single OST files

What it saves

MBOX first, plus EML, PDF, HTML, TXT

Who uses it

Outlook and Exchange users and admins moving or archiving mail

Conversion scope

OST to MBOX Converter for Offline outlook mail on Windows

OST to MBOX Converter Saves Every folder as an MBOX file

An OST file is the local mailbox copy that Outlook keeps. MBOX files import into Thunderbird and Apple Mail. OST to MBOX converter reads Outlook OST files on Windows and saves every folder as an MBOX file, with your OST files left as they were.

Kept in output

Email body and headers
Attachments
Sender and receiver
Dates and subjects
Folder tree

OST input types

Offline OST files
Orphaned OST files
Single OST files
Folders of OST files

Outputs

MBOX
EML
PDF
HTML
TXT
CSV
Gmail
Office 365
IMAP

Not needed

Outlook install
Internet connection
Mailbox password
Extra software

MBOX packs many emails into one file

RFC 4155 defines MBOX as many messages in one file, and Thunderbird still calls it the traditional format, as the Mozilla Thunderbird Maildir page says. An OST stays locked in Outlook, and the Microsoft overview of Outlook Data Files says Outlook cannot import from it. OST to MBOX converter saves every OST folder as MBOX and leaves the OST as it was.

Open MBOX file

Related pages: OST Converter, MBOX Converter, OST to EML Converter, PST to MBOX Converter and MBOX to PST Converter. Other mail files sit on email converter tool page.

Core features

OST to MBOX Converter Features by Screen

Five screens of Corbett OST to MBOX converter software, in conversion order.

OST to MBOX converter email data files list

Source files

Add Your OST Files

Select Open, then Email Data Files, and add your OST files. OST to MBOX converter loads your mail into its panel, and no Outlook is needed.

A spare PC with no Outlook still works. OST to MBOX converter reads your files and leaves them as they were.

Batch loading

Choose Files or Choose Folders

Select Choose Files for one OST file or a few. Select Choose Folders to load an entire directory of OST files in one step.

Loaded mail appears in one tree with a checkbox beside every item, so OST to MBOX converter handles many OST files in a single session. No file size limit applies.

OST to MBOX converter email preview with content, header, properties, hex and raw views

Message preview

Preview OST Mail Before Converting

Click any message and a reading pane opens beside five analysis views. Use them to confirm correct mail before OST to MBOX conversion starts.

Content shows the email body. Message header lists From, To, Subject and Date. Properties reports item data, while hex and raw message views show the stored mail.

OST to MBOX converter export menu with email file and document formats

Output formats

Select MBOX as Your Output Format

Select MBOX under Email Files in the Export menu. The same load also exports EML, PDF, HTML and more, and the menu lists Gmail, Office 365, IMAP and Thunderbird for sending mail into an account.

Search by keyword first, then save only matched items. Quick search highlights hits in yellow, and Advance search checks every field or only name, subject, To, Cc and content.

Export options

Set MBOX Export Options Before You Save

Switch on open folder after export, skip greyed out folders, create empty folders and include email headers. Every folder converts to its own MBOX file, so your tree stays in order.

Select Browse to choose a destination, then Save. Live progress shows every folder as it converts, and Open Folder takes you to your MBOX output.

Working process

How to Convert OST to MBOX in Four Steps

Four steps take your OST files to MBOX. Try them on a few files in free demo first.

Add your OST files

Start OST to MBOX converter, select Open, then Email Data Files and add your OST files. Select Choose Files for one file or Choose Folders for many.

Preview and select mail

Your OST folders load as one tree. Click any email to preview it, tick what you need and search by keyword to trim your OST to MBOX conversion.

Choose MBOX output

Select Export, then MBOX under Email Files. EML, PDF, HTML, TXT, CSV sit in the same menu for other jobs.

Save your MBOX output

Set options, select Browse for a folder and press Save. Live progress shows every folder, and Open Folder takes you to your MBOX output.

Moving the result into a client is covered in Import MBOX to Thunderbird account and Import MBOX to Apple Mail account.

Working process

OST to MBOX Converter Video Walkthrough

Prefer text? Open Import MBOX to Thunderbird account for the next move with your finished MBOX output.

Advanced options

More OST to MBOX Converter Features for Big Jobs

Small options that save hours when you convert OST files in bulk with OST to MBOX converter.

Bulk OST input

Many OST files convert in one session

Folder hierarchy

MBOX output follows your OST tree

No file size limit

Any OST size and mail count converts

Five preview views

Content, header, properties, hex and raw message

Advance search

Name, subject, To, From and content fields

Quick search

Yellow hit highlights in the preview

Chosen items

Convert contacts, addresses or attachments only

Attachment extraction

Save attachments alone, any size

Email address extraction

Save addresses to their own file

Empty folders option

Keep the full tree, even with no mail

Cloud upload

Send mail to Gmail, Office 365 or IMAP

USB and NAS targets

Save output to external drives and network storage

Output formats

OST to MBOX Converter Output Formats

OST to MBOX converter saves mail as MBOX, and the same load exports more targets. Match your format to where your mail will open.

MBOX

One file per folder for Thunderbird and Apple Mail

EML

One file for every message

PST

A fresh Outlook file

PDF

Readable pages for filing and records

HTML

Messages that open in any browser

TXT and CSV

Plain text and sheets of mail details

Gmail, Office 365 and IMAP

Mail lands in the target mailbox

Any drive

Local, USB and network folders

Free demo

Test OST to MBOX Converter on a Real OST File

Install free demo, load a OST file and choose MBOX. Free demo converts 10 emails per folder, so your output is quick to check.

Download free demo

Try before you buy

Free Demo vs Full OST to MBOX Converter

Free demo of OST to MBOX converter opens, previews and searches your full OST file. Only conversion is capped.

Feature	Free demo	Full version
Open OST files and folders	Yes	Yes
Preview and search	All available	All available
Emails converted per folder	10	Unlimited
OST size and mail count	Conversion stops at 10 per folder	No limit
Price	Free	From $99 one time

Use cases

Who Needs a OST to MBOX Converter?

Anyone who holds OST mail that will not open where needed.

Outlook and Exchange users switching programs

OST to MBOX converter saves mail as MBOX files that Thunderbird and Apple Mail import, so your mail opens in Thunderbird, Apple Mail and any client that imports MBOX.

IT admins

Convert a folder of OST files to MBOX in one batch and hand every user a ready tree.

Legal and compliance teams

Save mail with headers and attachments intact for review and discovery.

Archive keepers

Convert OST files that only one program opens into MBOX that more programs read.

Anyone with orphaned OST files

Open mail from an OST file that Outlook no longer opens and save it as MBOX.

Selective exporters

Search by sender or subject and save only the matching emails.

Why Corbett

Why Choose Corbett OST to MBOX Converter?

No subscription

Lifetime price from $99

Works offline

No sign-in and no upload

Originals stay safe

OST files open read only

envelope-fill

No Outlook needed

No size limit

Any OST size and mail count

Folders kept

Folders and subfolders stay in order

Smart search

Name, subject, To, From and content

30-day refund

Money-back window after purchase

Before conversion

OST to MBOX Converter Scope and Limits

OST to MBOX converter converts OST files into MBOX. Here is what that covers and where it stops.

Capability	Supported	What it means
File to file conversion	Yes	OST to MBOX, EML, PDF, HTML, TXT, CSV and more
Folder tree	Kept	MBOX output follows your OST folders
Outlook installed	Not needed	Files open on a PC with no Outlook
Source OST files	Read only	Output goes to a new folder and your originals stay as they were
Internet and passwords	Not needed	Conversion works offline on local files
Calendars, tasks and notes	Check output	Mail is the focus, so other item types may stay in the source file
Mac and Linux	No	OST to MBOX converter installs on Windows only

Manual route or tool

OST to MBOX Converter vs Manual Route

Here is where the manual route stops, and where OST to MBOX converter takes over.

Job	Manual route	OST to MBOX Converter
Cost	Free	From $99 one time
One email	Open and save by hand	Works too
MBOX file output	Not offered in Outlook	Folder mail in one file
Many OST files	Slow and error prone	Folders of OST files in one session
Folder tree	Often reshuffled	Same as the source
Search before export	Basic search only	Name, subject, To, From and content
Outlook installed	Often required	Not needed

Global recognition

OST to MBOX Converter Software Users Trust

Users rate Corbett OST to MBOX converter 4.6 out of 5 from 683 reviews, and these software directories list it.

CNET
Download.io
UpdateStar
TopSoftware Advisor
SaaSHub
Uptodown

Specifications

OST to MBOX Converter Specifications

Download details

Download size: 87.4 MB
Demo limit: 10 items per folder
Delivery: After payment, mail arrives with a download link and a licence key.
Licence: Personal: 5 machines. Business: 25 machines. Enterprise: 100 machines. Lifetime validity.

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System

Hard disk: 150 MB of free space
RAM: 4 GB of memory minimum
Processor: 1 GHz Intel Pentium minimum and 2.4 GHz advised
Interface: English
Input: OST files

Supported editions

Windows 11 (64 bit), 10, 8 and 7 in 32-bit or 64-bit, plus Windows Server 2016, 2012 R2 and 2008.

Start OST to MBOX converter with administrator rights.

Corbett has built Windows email utilities since 2020. Setup trouble and first-use questions go to our support desk.

User testimonials

OST to MBOX Converter Reviews

OST to MBOX converter shares 683 reviews on software index sites and customer feedback.

4.6 out of 5

Collected across 683 reviews from software indexes and customer feedback. Three reviews below are unedited.

Moved Outlook mail to Apple Mail

Really great software. I had to move my Outlook mails to Mac OS supported Apple mails. For that, I had to convert OST emails to MBOX format. This app helped get my work done.

Nick Larsson

Simple and fast

What I liked about this software was its simple UI and fast speed. Didn’t faced any trouble with using the tool, and moreover, it exported my OST files to MBOX format pretty quickly, too.

Sam Mitchell

Big job done swiftly

I was quite concerned as I had to export a lot of OST files to MBOX format in a short amount of time. Luckily, I found this OST to MBOX Converter tool, and it really helped getting done with my work swiftly.

Tom Price

Before conversion

Prepare Your OST Files for MBOX Conversion

Three short checks keep your OST to MBOX conversion clean.

Make a OST copy

Back up your OST files on a safe drive before you start. OST to MBOX converter opens files read only, and a spare copy keeps the original safe.

Choose all mail or chosen items

Convert every folder at once, or limit the job to the folders and items you need.

Leave space for output

MBOX files hold many emails apiece, so a large mailbox needs a destination disk with free room.

Need an OST file in Outlook later? Read Import OST file into Outlook.

Best practice

How to Keep Your OST to MBOX Conversion Safe

A conversion only helps if your mail arrives complete. Four habits keep your data safe through it.

Back up first

Copy your original OST files before you start. Keep 3 copies on 2 types of media with 1 copy off site.

Start with one file

Convert one small OST file with OST to MBOX converter and open a few emails in MBOX. Catch a wrong setting before a large job.

Check the count

Compare the message count in the folder tree with the mail in your output before you close the job.

Keep originals until checked

Store your source OST files until counts match. Delete them only after you open converted mail.

Common questions

OST to MBOX Converter FAQs

OST to MBOX converter steps, formats, limits and licence answers.

What is an OST to MBOX converter?

An OST to MBOX converter opens Outlook OST files and saves every folder as an MBOX file. Corbett OST to MBOX Converter does that offline on Windows, so OST file converter needs no Outlook.

How do I convert OST to MBOX?

Open OST to MBOX converter, select Open, then Email Data Files and add your OST file. Preview your mail, select Export, then MBOX under Email Files and press Save.

Can OST to MBOX converter open an orphaned OST file?

Yes. It reads the OST file directly, so an orphaned OST or one from a deleted profile still loads. It does not need the original Exchange account or Outlook.

Can I import an OST file into Thunderbird?

Not directly. Thunderbird imports MBOX, not OST. Convert the OST with OST to MBOX converter and import the MBOX files instead.

Can OST to MBOX converter move mail to Apple Mail?

Yes. Apple Mail imports MBOX, so the files from OST to MBOX converter load there after conversion.

Can OST to MBOX converter save attachments only?

Yes. A separate option saves attachments alone, with a file extension filter for specific types.

Does OST to MBOX converter keep email headers?

Yes. Headers stay with every message, and the Include email headers option adds them to the output.

Can OST to MBOX converter save OST mail as EML or PST instead?

Yes. EML and PST sit under Email Files in the same Export menu, next to MBOX.

Can OST to MBOX converter convert many OST files at once?

Yes. Select Choose Folders and load a directory of OST files, then OST to MBOX converter converts every file in one session.

Does OST to MBOX converter keep my folder tree?

Yes. MBOX output follows the order of your source folders, and the Create empty folders option keeps folders that hold no mail.

Does OST to MBOX converter keep attachments?

Yes. Attachments stay with every message, and a separate option saves attachments alone with a file extension filter for specific types.

Can OST to MBOX converter convert only some emails?

Yes. Advance search filters by name, subject, To, From and content, and OST to MBOX converter converts only matching mail.

Can OST to MBOX converter preview mail first?

Yes. Click any message and five views open: content, message header, properties, hex and raw message.

Can OST to MBOX converter send mail straight to Gmail or Office 365?

Yes. Gmail, Office 365 and IMAP sit in the Export menu. Sign in to the target account and the mail lands there.

Does OST to MBOX converter have a size limit?

No. OST to MBOX converter sets no size cap, and batch mode takes many files at once. Keep free disk space for your output.

Does OST to MBOX converter need Outlook?

No. OST to MBOX converter reads OST files on its own, so it works on a PC without Outlook.

Will OST to MBOX converter change my OST file?

No. OST to MBOX converter opens your files read only, and output goes to a new folder.

Does my OST data pass through Corbett?

No. Conversion happens on your PC with no upload. Corbett never sees your OST files or messages.

Does OST to MBOX converter work on a Mac?

No. OST to MBOX converter installs on Windows only. Copy your OST files to a Windows PC and convert them there.

How many emails can free demo convert?

Free demo of OST to MBOX converter opens your files, shows every folder and gives you every search and preview. Conversion stops at 10 emails per folder, enough to test your output before you buy.

Which Windows versions work?

Windows 11 (64 bit), 10, 8 and 7, plus Windows Server 2016, 2012 R2 and 2008. There is no macOS or Linux build.

How many PCs does one licence cover?

Personal licence covers 5 machines for $99, Business covers 25 for $299 and Enterprise covers 100 for $499. All three are one time payments with lifetime validity, 24/7 support and a 30 day refund.

OST guides

OST to MBOX Converter Guides for Common Jobs

Every page below covers one OST job and answers questions it raises.

Getting into the OST

Use the MBOX files

Convert OST to MBOX Today

Test OST to MBOX Converter on a spare OST copy first. Full access is from $99 in a single payment, and refunds are open for 30 days.

Download free demo Purchase now

87.4 MB · Windows 11 to 7 and Windows Server 2025 to 2008 · 30 day money back