This guide shows how to import MBOX into Outlook in 2026. Outlook cannot open MBOX directly, so you must use Thunderbird or Apple Mail as a bridge or convert to PST/EML first. It covers open MBOX file in Outlook, Thunderbird MBOX to Outlook, and Google Takeout MBOX to Outlook workflows.
Recommended Quick Steps (2026)
- Import MBOX into Thunderbird (Local Folders).
- Export messages to EML (ImportExportTools NG).
- In Classic Outlook, create a folder.
- Drag-drop EML into that Outlook folder (small batches).
- Export to PST (Outlook Data File).
- Optional: Open the PST in New Outlook (email-only).
Quick Answer (2026)
- Small mailbox: export to EML in Thunderbird, drag-drop into Classic Outlook, then export PST.
- Large mailbox or many folders: use a MBOX to PST converter to preserve hierarchy.
- Need PST output with SysCurve: Classic Outlook must be installed.
- New Outlook: you can add/open a PST (email only) via Settings -> Files -> Outlook Data Files -> Add file. PST support in New Outlook is limited; use Microsoft’s doc in Sources for the latest limitations.
- New Outlook: PST import into a mailbox is not available in New Outlook currently. Use Classic Outlook for import/export.
Before you start
- Back up the MBOX files before any conversion.
- Close Thunderbird/Outlook only when copying profile/MBOX files (not during the import/export steps).
- For large jobs, plan time and free disk space.
- Test with ~50 emails first to confirm the workflow.
Method comparison: import MBOX into Outlook
| Method | Best for | Best for size | Internet required? | Keeps folder hierarchy? | Needs Classic Outlook? | Risk |
|---|---|---|---|---|---|---|
| IMAP bridge (Gmail) | Small MBOX / free path | Small | Yes | Partial (labels can differ) | Yes (for PST export) | Medium (duplicates, slow sync) |
| MBOX -> EML -> Outlook | Local Folders, smaller mailboxes | Small/Medium | No | Partial (manual folder creation) | Yes | Medium (drag-drop limits) |
| SysCurve MBOX to PST Converter | Large mailboxes / business use | Large | No | Yes | Yes (for PST output) | Low |
Note: Manual drag-drop can change read/unread status or flags. Converters usually preserve more metadata.
Best method by scenario
| Scenario | Best method |
|---|---|
| Google Takeout archive | Method 2 (EML) or Method 3 for large archives |
| Many folders + hierarchy matters | Method 3 |
| No internet allowed | Method 2 or Method 3 |
| Need free + small mailbox | Method 1 |
Choose your method
- Need PST at the end: Method 2 or Method 3.
- No Classic Outlook installed: Method 1 (IMAP bridge) or export to EML/MBOX and move to a PC with Outlook.
- Large MBOX or many folders: Method 3.
- New Outlook user: do the import/export in Classic Outlook, then switch back.
New Outlook vs Classic Outlook (PST reality, 2026)
Classic Outlook is still the simplest for PST import/export workflows. New Outlook can open PST files (email only), but PST support in New Outlook is limited and has requirements; check Microsoft’s latest doc linked in Sources. New Outlook can export mailbox items to PST via Settings -> Files -> Export. Importing emails/contacts/calendar items from a PST is not available in New Outlook currently (you can only access emails in the PST and move them). Calendar and contacts stored in PST are not available in New Outlook.
Where are MBOX files stored in Thunderbird?
If you need to locate the actual MBOX files, check your Thunderbird profile:
- Windows: %APPDATA%\Thunderbird\Profiles\
- macOS: ~/Library/Thunderbird/Profiles/
- Linux: ~/.thunderbird/ (Profiles inside)
Some Linux installs store the profile under ~/.var/app/... (Flatpak).
Local mail is usually in Mail\Local Folders\ and IMAP mail is in ImapMail\. MBOX files are the files without extensions; .msf files are indexes only.
Apple Mail route (Mac users)
Apple Mail can import MBOX files (Mail -> File -> Import Mailboxes -> Files in mbox format). After importing, move the mail to an IMAP account or export to EML and continue the Outlook workflow on a Windows PC for PST export.
If you need a PST file, complete the final export step in Classic Outlook on Windows.
Method 1: Import MBOX to Outlook via Thunderbird and Gmail IMAP (bridge)
This method is useful when mail is in Thunderbird Local Folders and you need a free bridge. If the mail already lives on an IMAP server (Gmail, Outlook.com, Microsoft 365), add the same account to Outlook and export to PST instead of re-uploading.
IMAP decision (direct vs bridge)
- Already on IMAP: add the same account in Outlook and export to PST.
- Local Folders: upload via IMAP (bridge) or use Method 2/3.
Note: You need Thunderbird and Outlook installed. Gmail is used as an IMAP bridge in the example below.
Step 1: Import MBOX to Thunderbird
1. Open Mozilla Thunderbird on your computer.
2. Go to the Menu and select “Add-ons and Themes”.
3. In the Add-ons Manager, search for “ImportExportTools NG”.
4. Click “Add to Thunderbird” to install the add-on.
5. A dialog box will pop up asking to confirm the addition. Click “Add”.
6. Make sure “ImportExportTools NG” is enabled, then restart Thunderbird.
7. Right-click “Local Folders” and choose ImportExportTools NG -> Import mbox file -> Individual mbox files.
8. Select your MBOX files, then click “Open”.
9. Check “Local Folders” to verify the imported emails.
Step 2: Confirm IMAP access in Gmail
1. Personal Gmail: IMAP is already ON (you may not see an Enable/Disable toggle). Add Gmail using “Sign in with Google”.
2. Google Workspace: IMAP may be restricted by your admin. Check with IT if you can’t add the account.
3. Optional: If you see the “Forwarding and POP/IMAP” tab, IMAP should already be enabled.
Note: App passwords are only available with 2-Step Verification and may not appear for work/school or Advanced Protection accounts. Prefer “Sign in with Google” when available.
If you changed any settings, click “Save Changes”.
Step 3: Generate App Password (only if Google prompts you)
App passwords require 2-step verification. If Google blocks sign-in or Outlook keeps asking for a password, create an app password.
1. Click your profile icon and choose “Manage your Google Account”.
2. Open “Security” and enable 2-step verification.
3. Search for “App passwords” and open it.
4. Create an app password (name it “MBOX to Outlook”) and copy it.
5. Save the app password securely.
Step 4: Configure Gmail in Thunderbird
1. Open Thunderbird and go to Account Settings.
2. Use Account Actions -> Add Mail Account, then enter your Gmail address and app password.
3. Select IMAP and finish setup.
Step 5: Upload MBOX emails to Gmail
1. Open your Gmail mailbox in Thunderbird and create a new folder.
2. Copy emails from Local Folders into the Gmail folder.
Step 6: Configure Gmail in Outlook and export PST
1. Add the Gmail account in Outlook, then select the Gmail folder and wait for Outlook to sync.
2. Export to PST: File -> Open & Export -> Import/Export -> Export to a file -> Outlook Data File (.pst).
Limitations (IMAP bridge)
- Slow for large MBOX files; upload and sync can take hours or days.
- Gmail labels can create duplicates if the same message exists under multiple labels.
- Also disable “Show in IMAP” for labels you don’t need (Gmail settings) before syncing if duplicates explode. Gmail (web) -> Settings -> See all settings -> Labels -> (label) -> Show in IMAP (toggle).
- Gmail tip: avoid copying from All Mail; copy label-by-label to reduce duplicates.
- Read/unread and flags can change during sync.
- Requires a Gmail account and internet upload.
Method 2: Convert MBOX to EML and import into Outlook (offline/manual)
This is the most direct manual method to open an MBOX file in Outlook without IMAP. It works best for Local Folders and smaller mailboxes.
Step 1: Export Thunderbird folders to EML (bulk)
ImportExportTools NG imports into Local Folders, not IMAP folders. Export folder-by-folder to preserve hierarchy.
- In Thunderbird, right-click a folder under Local Folders.
- Choose ImportExportTools NG -> Export all messages -> EML format.
- Repeat per folder to keep the same structure.
Do not export/import while Thunderbird is still indexing or compacting folders; finish background activity first.
Step 2: Import EML into Classic Outlook
- Create a matching folder in Outlook.
- Open the EML folder in File Explorer.
- Drag-drop in smaller batches (200-500) and wait for indexing.
If drag-drop fails: try smaller batches (50-100) or split by date.
- Disable Outlook add-ins temporarily if drag-drop freezes.
- Wait for indexing to finish before the next batch (or pause indexing during import).
- If read/unread status changes, use Method 3 for better metadata preservation.
If Outlook still freezes: import fewer EMLs (25-50), restart Outlook, and try again. If EML import is consistently unreliable or metadata matters, use Method 3.
Step 3: Export PST from Outlook
File -> Open & Export -> Import/Export -> Export to a file -> Outlook Data File (.pst). Select the folder and include subfolders.
Limitations
- Folder hierarchy must be recreated manually unless you export/import folder by folder.
- Large batches can freeze Outlook; keep batches small.
- Read/unread status and flags may not transfer perfectly.
Google Takeout MBOX to Outlook (quick notes)
Google Takeout exports Gmail as MBOX files. Import the MBOX into Thunderbird Local Folders, then use Method 2 (EML export) or Method 3 (converter) to import into Outlook.
Import MBOX to Outlook 365 / Microsoft 365 (notes)
Outlook and Microsoft 365 do not open MBOX directly. Convert MBOX to PST in Classic Outlook, then import that PST into your Microsoft 365 mailbox if needed.
For organizations/admins: Microsoft provides a PST Import service in the Purview portal (network upload with AzCopy + mapping file + import job).
Method 3: Convert MBOX to PST using SysCurve MBOX to PST Converter
Instant Solution - SysCurve MBOX to PST Converter
Convert MBOX to PST with folder hierarchy, attachments, and preview.
Use the SysCurve MBOX to PST Converter when you need speed and full folder preservation for large mailboxes. It exports to PST, EML, MSG, and HTML. For PST output, Outlook (Classic) must be installed on the same Windows PC. Outlook does not need to be open during conversion.
- Keeps folder hierarchy and attachments.
- Preview emails before export.
- Exports to PST, EML, MSG, and HTML.
Steps:
1. Download and install the SysCurve MBOX to PST Converter.
2. Open the tool and click “Add File”.
3. Select “Load Thunderbird Profile” or load MBOX files, then click “Upload”.
4. Select a folder to preview emails.
5. Click “Export”, choose PST as the export format, and select folders.
6. Choose the destination path.
7. Click “Export” to start the conversion.
8. Click “OK” when the export completes.
What transfers and what does not
| Method | Folder hierarchy reliability | Attachments | Inline images / HTML | Read/unread | Flags/categories | Dates | Rules/filters | Contacts/calendar |
|---|---|---|---|---|---|---|---|---|
| IMAP bridge | Partial | Yes | Usually kept | May change | May change | Usually kept | No | No |
| EML drag-drop | Manual | Yes | Usually kept | May change | May change | Usually kept | No | No |
| SysCurve converter | Yes | Yes | Yes | Better preserved | Better preserved | Preserved | No | No |
Troubleshooting (Most common failures)
- ImportExportTools NG option missing/greyed out: use Local Folders (not IMAP folders).
- Outlook drag-drop imports EML as attachments: create the Outlook folder first and retry smaller batches.
- Outlook freezes while importing EML: import 25–100 emails per batch and wait for processing to finish.
- EML drag-drop missing attachments / broken inline images: try smaller batches and export as “Messages (Attachments Embedded)”.
- Outlook drag-drop is slow: disable add-ins temporarily and let indexing finish before the next batch.
- ImportExportTools NG not installing: confirm Thunderbird version compatibility and reinstall from the add-ons page.
- Gmail duplicates after IMAP bridge: avoid All Mail and sync label-by-label.
- Too many simultaneous connections: Gmail may throttle; wait and retry smaller batches.
- Folder size limits / only sync small folders: split folders or export EML instead.
Frequently Asked Questions
Can Outlook open MBOX directly?
No. Outlook does not support MBOX, so you must convert to PST/EML or use an IMAP bridge.
Can I import MBOX into New Outlook?
Not directly. Use Classic Outlook for the import/export steps. See the New Outlook PST reality box above.
Do I need Outlook installed to create a PST?
Yes for manual methods and SysCurve PST output. Without Outlook, export to EML/MBOX and convert later on a PC with Outlook.
What is the best method for Google Takeout MBOX to Outlook?
Import the MBOX into Thunderbird Local Folders, then use Method 2 or the SysCurve converter for large archives.
Does drag-drop keep read/unread status?
Not always. Read/unread and flags can change during drag-drop; converters usually preserve more metadata.
Does Outlook for Mac use PST?
No. Outlook for Mac uses OLM, not PST. Use a Windows PC for PST export.
Why is ImportExportTools NG import greyed out?
ImportExportTools NG works on Local Folders. If you right-click an IMAP folder, options can be disabled.
Can I keep Thunderbird folder hierarchy?
Yes. Export folder-by-folder or use a converter that preserves hierarchy automatically.
Related guides
- How to convert MBOX to PST
- How to convert Thunderbird to PST
- How to convert EML to PST
- Google Takeout MBOX to Outlook
Sources
- Microsoft: Open and find items in an Outlook Data File (.pst)
- Microsoft: Feature comparison between new Outlook and classic Outlook
- Microsoft: Create an Outlook Data File (.pst)
- Microsoft Purview: Import PST files (network upload)
- Mozilla: Where Thunderbird stores user data
- Thunderbird add-on: ImportExportTools NG
- Google: Sign in with app passwords (requires 2-step verification)
The final word
MBOX to Outlook conversion is easiest when you pick the right method. Use IMAP for small mailboxes, EML export for local folders, and a converter for large archives and preserved hierarchy. Always verify a sample of messages after export and keep a backup of the original MBOX.
