MBOX to PST Converters Compared: 5 Tools Tested on Windows and Mac

Moving email archives between clients shouldn't require a computer science degree. But MBOX (used by Thunderbird, Apple Mail, and others) and PST (Outlook's format) don't play nicely together — you need a converter.

The problem: most "reviews" just list five tools with identical vague praise. This comparison covers what actually matters: pricing, file size limits, attachment handling, and folder structure preservation.

Quick Comparison

All tools are one-time purchases, not subscriptions. Pricing checked as of late 2023 — verify before buying.

Outlook Transfer

Outlook Transfer positions itself as a straightforward solution for users who want to convert MBOX to PST for Outlook without wrestling with complex settings.

What works well:

• Clean interface that doesn't overwhelm new users
• Preserves folder hierarchy during conversion
• Handles attachments reliably, including inline images
• Separate Mac version available (not just Windows emulation)

Limitations:

• Free trial restricts conversion volume
• No preview before conversion in basic mode
• Requires Outlook installed on Windows (uses Outlook as intermediate step)

Best for: Users migrating personal email archives to Outlook who want a simple, guided process.

Pricing: $25 for single license. Reasonable for one-time migration needs.

Cigati MBOX Converter

Cigati targets users handling multiple mailbox formats, not just MBOX-to-PST. The same tool converts to EML, MSG, PDF, and other formats.

What works well:

• True cross-platform support (native Mac app, not Wine-based)
• Converts to multiple output formats in one pass
• Maintains email metadata (dates, read/unread status, flags)
• Handles large MBOX files without crashing

Limitations:

• Interface feels dated compared to competitors
• Free trial limited to 25 emails per folder — barely enough to test properly
• Support response times vary

Best for: Users who need format flexibility beyond just PST, or who manage multiple archive types.

Pricing: $49. Higher than some alternatives, but the multi-format capability justifies it if you need those features.

Kernel MBOX to PST Converter

Kernel (from Nucleus Technologies) focuses specifically on the MBOX-to-PST workflow rather than trying to be a universal converter.

What works well:

• Fast conversion even with large archives (10GB+ tested)
• Accurate folder structure mapping
• Filters by date range — useful for partial migrations
• Splits large PST files automatically (avoids Outlook's 50GB limit issues)

Limitations:

• Windows only — no Mac version
• Requires Outlook installed for direct import option
• 25-item trial is too restrictive to evaluate properly
• Occasional issues with non-English characters in folder names

Best for: Windows users doing large-scale migrations who need speed and PST splitting.

Pricing: $39. Mid-range, good value for the speed and splitting features.

SysInfo MBOX Converter

SysInfo offers a capable converter with a focus on maintaining email integrity during migration.

What works well:

• Preserves email headers completely (important for legal/compliance archives)
• Handles nested folder structures well
• Exports to both PST and directly to Office 365
• Supports orphaned MBOX files (no email client installation required)

Limitations:

• Interface is cluttered with upsells for other SysInfo products
• Mac version has fewer features than Windows
• Documentation could be clearer
• Same restrictive 25-item trial

Best for: Compliance-focused migrations where header preservation matters, or Office 365 migrations.

Pricing: $49. Fair for the Office 365 integration, which competitors charge extra for.

Stellar Converter for MBOX

Stellar has name recognition from their data recovery tools. Their MBOX converter maintains that reputation for reliability.

What works well:

• Most polished interface of the five
• Preview emails before conversion (helpful for selective migration)
• Technician license allows use on multiple machines
• Good handling of corrupted MBOX files

Limitations:

• Separate purchases required for Windows and Mac
• Technician license pricing jumps significantly ($149)
• Some features require Outlook to be installed
• Slower than Kernel on very large files

Best for: Users migrating partially corrupted archives, or IT professionals needing multi-machine licenses.

Pricing: $39 single license, $149 technician. The base price is competitive; the technician tier is expensive.

Why Convert MBOX to PST?

Before buying software, confirm you actually need this conversion. Common scenarios:

Switching from Thunderbird/Apple Mail to Outlook

The most common reason. Outlook doesn't read MBOX files natively, so conversion is unavoidable. If you're moving to Outlook, you need PST (or direct import to an Exchange/Office 365 account).

Corporate standardization

Organizations consolidating on Microsoft 365 often need to migrate employee archives from various email clients. PST serves as an intermediate format for importing into Exchange Online.

Archiving for legal/compliance

Some industries require email retention in specific formats. PST files integrate with eDiscovery tools and legal hold systems better than MBOX in Microsoft-centric environments.

Backup consolidation

If you've accumulated MBOX exports from multiple sources over the years, converting to PST creates a single searchable archive accessible in Outlook without maintaining multiple email clients.

Free Alternatives (With Caveats)

Before paying for conversion software, consider these options:

Import via IMAP workaround:

1. Set up a temporary IMAP account (Gmail works)
2. Connect both your MBOX-based client and Outlook to that account
3. Copy emails to the IMAP server from the source client
4. Download them in Outlook

This works but is slow for large archives and requires stable internet throughout.

Thunderbird + ImportExportTools NG:

A free Thunderbird add-on that exports to EML format. Outlook can import EML files, though you'll lose folder structure and need to reorganize manually. Workable for small archives, painful for large ones.

Manual conversion via Python scripts:

If you're comfortable with code, Python's mailbox library reads MBOX files. Combined with pypff for PST writing, you can script custom migrations. Only recommended if you have specific requirements the commercial tools don't meet.

Choosing the Right Tool

Budget-conscious, simple migration: Outlook Transfer ($25) handles basic needs at the lowest price point.

Need multiple output formats: Cigati ($49) offers flexibility beyond just PST.

Large archives, Windows only: Kernel ($39) provides the best speed and automatic PST splitting.

Office 365 destination: SysInfo ($49) includes direct cloud migration.

Corrupted source files: Stellar ($39) handles damaged MBOX files better than alternatives.

Mac users: Cigati or SysInfo have the most complete Mac implementations. Outlook Transfer's Mac version works but has some limitations.

Before You Convert

A few practical tips regardless of which tool you choose:

Back up your MBOX files first. Conversion tools don't modify originals, but having a backup prevents disasters.

Check your MBOX file locations:

• Thunderbird (Windows): %APPDATA%\Thunderbird\Profiles\[profile]\Mail\
• Thunderbird (Mac): ~/Library/Thunderbird/Profiles/[profile]/Mail/
• Apple Mail: ~/Library/Mail/V[version]/

Test with a small batch. Even with paid tools, convert a single folder first to verify attachments and formatting transfer correctly.

Consider PST file size. Outlook handles PST files up to 50GB, but performance degrades above 10-20GB. If your archive is larger, use a tool that splits output files automatically.

For other file format conversions — like encoding images for web applications — similar principles apply: test with sample data, verify output integrity, and keep source backups.

Bottom Line

All five tools accomplish the basic task of converting MBOX to PST. The differences lie in pricing, platform support, and edge-case handling.

For most personal migrations, Outlook Transfer or Kernel offer the best value. Corporate users should evaluate SysInfo's Office 365 features or Stellar's multi-machine licensing.

Don't overthink it — pick based on your platform and budget, test with the trial version, and move on. The conversion itself takes minutes; choosing the "perfect" tool shouldn't take hours.