Updated 16 September 2026
MBOX to PST converter features
Convert one MBOX file or a folder tree to PST for classic Outlook. Keep folders and attachments, filter messages, and split large results into smaller PST files.
Which mailbox files can I convert?
Select one MBOX file, a folder of MBOX files, or a parent folder with subfolders. Common sources include Thunderbird, Apple Mail, and Google Takeout. Extract ZIP or TGZ downloads before selecting the MBOX files inside.
First confirm that your source really uses MBOX; renaming another kind of file will not convert it. The MBOX and PST comparison explains what the utility can move.
What will the PST contain?
The converter keeps message text, formatting and attachments together, and can recreate your mailbox folders in the PST. If you need Internet headers—the technical delivery details stored with a message—turn on Add Internet headers.
Before converting a large archive, test a small but varied copy. Check old and recent messages, sender and recipient details, accented or non-Latin text, pictures inside messages, and several attachment types. Keep the original MBOX files until you have checked the converted PST.
How can the PST output be organized?
Swipe or scroll to compare all columns.
| What you want | Option to use | What to check afterward |
|---|---|---|
| Keep source mailboxes separate | Create a folder for each source MBOX | Folder names and nesting |
| Keep each PST below a chosen size | Maximum PST file size | Every numbered PST opens in Outlook |
| Add mail to a PST you already have | Write to an existing PST | Correct destination folder and no repeated messages |
| Keep Gmail labels | Create folders or categories from Google labels | Messages that had more than one label |
| Build output names from message details | Filename macros, if your license includes them | Resulting names and license choice |
Two size settings have different effects. Maximum PST file size starts another PST file when the current one reaches your chosen limit. Skip files greater than leaves an entire source MBOX file out of the conversion. Review the skipped files before deciding that the job is complete.
Can I choose which mail to convert?
Convert all messages, only messages with attachments, or only messages without attachments. You can also skip MBOX files above a chosen size. Note any filter you use so a smaller PST is not mistaken for missing mail.
The utility can move each completed MBOX file to another folder so it is not processed again later. This does not find messages repeated across overlapping exports. Converting the same source into an existing PST can also create duplicates.
When do I need Professional?
You do not need Professional simply because a mailbox is large. This paid edition is for automation: it can run the converter from a typed or scripted command and through Windows Task Scheduler at set times. Professional also supports activation on Windows Server.
Some naming options use parameter macros, placeholders that insert details such as a date or mailbox name into an output name. Macros and integration with Outlook rules depend on the license edition. Compare the license table before buying.
Does my mail stay on my computer?
Conversion runs on your Windows computer and requires a supported classic Outlook installation. The Outlook window can stay closed. The utility reads exported files, so it does not need the original mail-account password.
Your mailbox stays on the computer or storage path you choose during conversion. Downloading the installer, activating a license, checking for updates, or contacting support can still use the internet. See the system requirements and security and privacy guide.
Convert MBOX to PST is developed by Relief Software and licensed by Relief, LLC under the ReliefJet brand. See our product documentation for conversion options and instructions.
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.