What should You Prepare Before You Import?
- Copy the MBOX files to a safe folder.
- Remove the .mbox extension if the file has one and the file copy method applies.
- Find the Local Folders account in the Thunderbird folder pane.
- Check that the file came from a real mail export, like Google Takeout or Apple Mail.
Mozilla support answers advise importing into Local Folders and not into an IMAP account folder. Move the messages to the IMAP account afterward.
How does the Add-On Import MBOX Files?
Method #1: Add-On Import (Free)
Who it suits. Users with one or a few MBOX files. Extra application. A Thunderbird add-on.
- Open Thunderbird and install the add-on from Add-ons and Themes.
- Restart Thunderbird and select Local Folders.
- Open Tools, then ImportExportTools NG and Import mbox file.
- Select Import directly one or more mbox files, or choose the subdirectory option for folders.
- Browse to the MBOX file and select Open.
Mozilla support threads show a common slip. The import menu stays silent until you select Local Folders first. Right click Local Folders and open the add-on menu if the Tools menu does nothing.
Can You Copy the File Into the Profile?
Method #2: Manual File Copy (Free)
Who it suits. Users who cannot install add-ons. Extra application. None.
- Open Thunderbird, select Help, then Troubleshooting and show the profile folder.
- Close Thunderbird.
- Copy the MBOX file, with no extension, into the Mail\Local Folders folder.
- Start Thunderbird and look for a folder with the same name under Local Folders.
This method works for plain MBOX files only. Ignore the .msf files that sit next to them.
What if the Add-On Fails or You have Many Files?
Method #3: Thunderbird Import Wizard (Paid After Demo)
Who it suits. Users with bulk files, large archives or IMAP accounts. Extra application. Thunderbird Import Wizard.
The Thunderbird Import Wizard imports MBOX, MBS, MBX, EML, EMLX and Maildir files into POP, IMAP or Local Folder profiles.
It detects configured profiles, retains folder structure and read status, filters by date and sets no file size limit. For IMAP accounts, import into Local Folders first and drag the folder across. Thunderbird must be installed, and you restart it to see the data.
Windows trial imports 25 items per folder. The Mac trial imports the first 10 emails per MBOX file.
What should You do After the Import?
- Open the new folder and check message counts.
- Search for a known message and open an attachment.
- Drag the folder to your IMAP account if you want server sync.
- Retain the original MBOX files until you finish the checks.
Going the other way? Our guide to import Thunderbird to Outlook and the MBOX file guide help with that move.
Frequently Asked Questions
Does Thunderbird Import MBOX Files by Default?
No. Most users install the ImportExportTools NG add-on and import into Local Folders.
Why does the Import Menu do Nothing?
Select Local Folders first, or right click Local Folders and use the add-on menu.
Can You Import MBOX Into an IMAP Account?
Import into Local Folders first, then move the folder to the IMAP account.
Do You Need to Remove the .mbox Extension?
Remove it only for the manual file copy method. The add-on accepts the file as it is.
How do You Open the Profile Folder?
Select Help, then Troubleshooting, and show the profile folder.
Which Formats does the Import Wizard Accept?
The vendor page lists MBOX, MBS, MBX, EML, EMLX and Maildir files.
How do You Import MBOX Files From Google Takeout?
Unzip the download, then import the MBOX file into Local Folders with the add-on.
Author's Verdict
Start with the add-on, because it is free and takes minutes.
Use the wizard for bulk files, IMAP targets or an add-on that fails.
Key Takeaways
- Select Local Folders before you import.
- The manual copy needs a file with no extension.
- Backup the MBOX files first.
Related Guides
Using Outlook instead? See how to import an MBOX file into Outlook.