Updated 17 September 2026
System requirements
To convert MBOX files, use a Windows computer with classic Microsoft Outlook and .NET Framework 4.0 or later installed. New Outlook and Outlook on the web cannot replace classic Outlook for this conversion.
Operating system
- Windows 11, Windows 10, Windows 8/8.1, Windows 7, Windows Vista, or Windows XP SP3.
- Windows Server 2003 R2 through Windows Server 2025. Server activation requires a license that permits Windows Server; choose Professional if you need this option.
Microsoft no longer supplies security updates for several older versions, so use a version that Microsoft still supports whenever possible.
Windows 11 requires a 64-bit processor. Windows architecture and Outlook bitness are separate requirements. This list does not establish converter compatibility with Windows on ARM; check your configuration with us before choosing it.
Microsoft Outlook
- Classic Outlook for Microsoft 365, or Outlook 2024, 2021, 2019, 2016, 2013, 2010, or 2007.
- Both 32-bit and 64-bit Outlook are supported for Outlook 2010 and later.
- New Outlook for Windows is not supported. Outlook on the web also cannot perform the conversion.
- Classic Outlook must be installed on the same computer as the converter. Its window can stay closed while the standalone utility runs.
Runtime and installation
- Microsoft .NET Framework 4.0 or later. This is a Windows component the utility needs in order to run; the installer prompts you if it is missing.
- About 10 MB of free space for the application itself. The source copy, temporary work, and PST files require additional space.
- A normal installation for one Windows user does not require administrator rights.
Disk space
Create the working PST on a local drive outside OneDrive or other synced folders. After checking it, close Outlook and the converter before copying the file to network or cloud storage as a backup.
On the drive where you will save the PST, start with at least as much free space as the source MBOX files occupy. Leave extra room for temporary work and for the additional information Outlook stores inside a PST. The exact PST size varies with attachments, message details, and folder structure.
For a large mailbox, use Maximum PST file size on the Advanced tab to create several smaller PST files. A value of 0 allows one PST to grow without a limit set by the utility; a positive value starts a new PST at that size. Outlook still applies its own limits. Microsoft documents a default 50 GB limit for the modern Unicode PST format in Outlook 2010 and later, but very large files can become slow before reaching that limit. Follow the steps to split the result by size instead of aiming for 50 GB. See Microsoft’s PST size-limit documentation.
What is not required
- The conversion itself does not need an internet connection because the mailbox is processed on the computer.
- You do not need the original mailbox password or access to the live account. The utility reads the exported MBOX files.
For installation details, see our system requirements documentation. Not sure whether your Windows and Outlook versions will work together? Send us the exact version numbers before buying.
Open your MBOX email in Outlook
Download the Windows converter and try it with a copy of your mailbox. You will need classic Outlook installed on the same computer.