Microsoft Outlook
ReliefJet ESSENTIALS™
for Microsoft Outlook
ReliefJet Essentials for Outlook is a comprehensive set of more than 150 tools for performing a wide range of tasks in processing email messages, contacts, appointments, meetings, tasks and other Outlook items as well as Office 365 or Exchange Server folders and mailboxes.
ReliefJet Essentials™
for Microsoft Outlook
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Convert PST to MBOX

Most email clients support importing messages from MBOX files, but they don't work with PST files, which are only used in Microsoft Outlook. This utility converts email messages from PST data files into MBOX format compatible with many email programs and systems.

What is an Outlook PST data file?

Microsoft Outlook uses the PST file format to store its data such as messages, contacts, appointments and meetings, tasks, notes, documents, journal entries, etc. All data can be located in folders of distinct types: mail, calendars, and others. Besides, PST files store important additional properties of Outlook items and folders. For example, rules and alerts, view settings, or search folders.

Therefore, when transferring data from PST to another location, it is necessary to properly process the information stored in them. By simply copying PST files, you can cause Outlook to malfunction.

What is an MBOX file?

The MBOX email database format is used by mail systems for Windows, MacOS, Linux and Unix. This format is used by popular mail apps: Thunderbird, Apple Mail, Eudora, Entourage, Postbox, PocoMail, Netscape, Spicebird, Claws Mail, Opera, PowerMail, Sylpheed, Evolution, SeaMonkey, Mulberry, GyazMail, Sparrow, Gnu, The Bat! and others.

MBOX files do not contain folder structure, so each message folder is usually stored in a separate MBOX file.

Why convert PST to MBOX?

There are several reasons for PST2MBOX conversion:

  1. PST is an internal Outlook format. No other email client works with this format. To use a different email client instead of Outlook, you need to convert your PST files to the format this program can use.
  2. Microsoft Outlook is a big and complex program. This is not just a mail client, but a corporate organizer with tasks, contacts, calendars, and many more. Most users don't need as many features to work with their personal email. That's why they choose simple mail apps that don't take much time to learn.
  3. Outlook is a paid product. After the free trial period expires, you must purchase it. This is one of the many reasons people choose to use other, free email clients.
  4. The MBOX format is supported by many mail applications, but you can't get it directly from Outlook, so you will need our converter.

Why can’t you use online services to convert PST to MBOX?

Outlook PST files contain your important confidential data. When you use an online service to convert mail from PST to MBOX, all your data is transferred to someone else's server, including private messages, contacts, tasks, and notes. The data is processed on someone else's computer, and you can't control it. Only then can you download your emails in MBOX format. Also, the size of PST files can reach dozens of gigabytes and uploading such files will take a long time - if possible at all.

In contrast to online converters, our utility works strictly on your computer. No information is transferred anywhere. With this tool, your data will not fall into the wrong hands.

"Convert PST to MBOX" Screenshots
Convert PST to MBOX

How to convert PST to MBOX?

  1. Select the source PST file or folder with PST files and specify the destination folder.
  2. Run the utility and all further work will be done automatically.

The tool allows you to create separate folders for each PST file, create a folder structure from folders inside PST files, set filters by dates, sent or received status, and use macros for file and folder names.

Is it possible to customize MBOX file names when converting from PST?

The short answer is yes!

If you simply specify a folder for MBOX files, all converted messages will be saved to this folder. And messages from each Outlook mail folder will be saved to a separate MBOX.

Additionally, the utility allows you to flexibly configure the names of the resulting folders and MBOX files. To do this, you can use macros in the target path: e.g. message subject, sender and recipient names or domains, sending and receiving dates, current date and time, Windows environment variables and many other values.

For advanced users, there are regular expressions to extract only the necessary parts of the subject, message text, and other message fields for the target file and folder names.

Are there any limits when converting from PST to MBOX?

There are no limits on the number and size of resulting files and files to be converted. You can convert an unlimited number of folders or files as often as you want.

Since MBOX is a format for storing email messages only, no contacts, calendars or other Outlook items will be saved in it.

When converting, the utility saves all available data, such as:

  • message subject,
  • send and receive dates,
  • sender and recipient addresses,
  • message text with HTML markup,
  • attachments and images,
  • message flagged or starred,
  • read/unread and replied/forwarded status,
  • Internet headers.

How to perform mass PST conversion to MBOX?

The command line in the product provides the ability to convert a large number of PST files to MBOX in bulk using scripts, batches, PowerShell, and other automation tools. The command-line application will help you to implement complex email migration scenarios. Automatic conversion of PST files to MBOX is faster if you run multiple command-line apps simultaneously.

To convert PST to MBOX by schedule, use the product's command-line and the standard Windows Task Scheduler. This allows you to flexibly configure the schedule settings and use the program automatically even without interactive login to the user account.

By converting your email from Outlook PST data files to MBOX message databases, you will get separate files for each Outlook folder according to the original folder structure. After that, you can import the resulting MBOX files to other mail clients.


Described features are part of ReliefJet Essentials for Microsoft Outlook: fast and reliable productivity solution for Microsoft Outlook. Besides them ReliefJet Essentials provides many other useful features that significantly simplify every Outlook user's life. An Outlook add-in and a command line utility are also provided along with the standalone application.

Related Utilities: Export Messages to MBOX, Convert PST to EML, Convert MBOX to PST.

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      Best Value!    
    Single Utility License Personal Edition Professional Edition  
Number of utilities available 1 All 159 included All 159 included
Key Features
Integration with Outlook rules No Yes Yes
Macros for utility parameters No Yes Yes
Command line support No No Yes
Integration with Task Scheduler No No Yes
Support for Windows Server OS No No Yes
Support and Updates
Product support 1 Year 2 Years Lifetime
Free updates No 1 Year 2 Years
Free remote assistance No Yes Yes
Free script writing assistance No No Yes
Price Per License
1 license purchase $19.95
($19.95 per utility)
$49.95
($0.31 per utility)
$199.95
($1.26 per utility)
2-9 licenses purchase $14.95 $34.95 $129.95
10+ licenses purchase $9.95 $19.95 $99.95
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Compatible with Windows 10