Written by Jennifer Walsh. Reviewed for technical accuracy by Shubham Dixit, Independent Expert in Email Forensics and Data File Conversion.
Shubham is an independent external reviewer and not an employee of PCDOTS.
Quick answer. Thunderbird already stores each folder as a single MBOX file, so exporting is really just getting that file out. The free way is the ImportExportTools NG add-on, right-click a folder and export it as a .mbox. You can also copy the file straight from your profile. A tool helps mainly if you also want other formats, or a copied profile with no Thunderbird.
On this page
Thunderbird already is MBOX
Here is the part that makes this easy. Thunderbird does not need converting to MBOX, because it already stores each folder as a single MBOX file inside your profile. So when you want to export the MBOX, you are not really converting anything, you are just pulling that file out cleanly and giving it the .mbox name. That is why this is one of the simpler jobs, not a difficult one.
There is a free add-on that does the pulling-out neatly, and if you prefer, you can copy the file from the profile by hand. Both give you a complete .mbox, attachments and all.
You are not converting, the folder is already MBOX, you just pull the file out.
“There is a myth that exporting MBOX from Thunderbird risks losing data or attachments. It does not. Thunderbird keeps the folder as an MBOX already, and the ImportExportTools NG add-on simply writes that out, complete message with its attachments intact. I would only reach for a converter when the goal is really something else, you also want PST or PDF, or you are working from a copied profile with no Thunderbird to open. For plain Thunderbird to MBOX, the free add-on is the honest answer.” Shubham Dixit, Data Migration reviewer (draft, pending approval)
Free, the ImportExportTools NG add-on
This is the clean free way, and it is the one most people want. ImportExportTools NG is a free Thunderbird add-on that exports a whole folder to a .mbox in a couple of clicks.
In Thunderbird open the Add-ons manager, search for ImportExportTools NG, and add it. Then right-click the folder you want, choose ImportExportTools NG, then Export folder, and pick a destination. It writes the folder out as an MBOX file, and if it does not already carry the extension you can rename it to .mbox. The file is a full copy of the folder with every message and attachment, there is no data loss.
Install, right-click the folder, Export folder, and you have your .mbox.
No add-on, straight from the profile
If you would rather not install anything, you can take the file Thunderbird already keeps. Go to Help, Troubleshooting Information, and next to Profile Folder click Open Folder. Inside, under Mail or ImapMail and your account, each folder is a file named like the folder with no extension, that file is the MBOX. Copy it out, and add .mbox to the name. Quit Thunderbird first so the file is not in use. It is the same complete mailbox, just taken by hand.
When a tool actually helps
To be straight about it, for plain Thunderbird to MBOX you do not need to buy anything, the free routes above are the whole job. A tool earns its place only in a few cases, when you also want other formats like PST, EML or PDF from the same mail, when you are working from a copied profile with no Thunderbird to open, or when you want to run many folders or accounts at once with filtering. For those, the PCDOTS Thunderbird Converter reads Thunderbird’s files and exports to MBOX and other formats on Windows, with a free version that handles the first ten items per folder.
The tool route, for other formats or a copied profile, not because free loses data.
Here are the steps with the screens.
Step 1. Install and run the software on Windows, then open the menu.
Step 2. Choose Desktop Email Clients, Thunderbird, and load the account.
Step 3. Open the Export menu and choose MBOX.
Step 4. Choose a destination folder and Save.
Once you have the .mbox, our guide to convert MBOX files to EML covers what to do with it next, and for the other direction see convert Thunderbird emails to EML or import MBOX into Thunderbird.
The methods compared
For plain Thunderbird to MBOX, the free routes are all you need. The tool is for the wider cases.
| Method | Best for | Good to know |
|---|---|---|
| ImportExportTools NG | The usual free way | Export folder, complete .mbox |
| Copy from the profile | No add-on wanted | Quit Thunderbird, add .mbox |
| Thunderbird Converter | Other formats or a copied profile | Windows, bulk with filters |
Frequently asked questions
Does Thunderbird store mail as MBOX already?
Yes. Each Thunderbird folder is kept as a single MBOX file in your profile, so exporting is really just taking that file out and naming it .mbox.
What is the free way to export MBOX from Thunderbird?
Add the free ImportExportTools NG add-on, right-click the folder, choose Export folder, and save. It writes a complete .mbox with attachments.
Does the free method lose data or drop attachments?
No. The exported .mbox is a full copy of the folder, so every message and its attachments are included. There is no data loss.
Can I get the MBOX without any add-on?
Yes. Quit Thunderbird, open the profile folder from Help then Troubleshooting Information, and copy the folder’s file from Mail or ImapMail, then add the .mbox extension.
Where does Thunderbird keep the MBOX files?
In your profile, under Mail for local and POP folders or ImapMail for IMAP accounts. Each folder is a file named like the folder with no extension.
When is a converter worth it?
When you also want other formats such as PST, EML or PDF, when you only have a copied profile with no Thunderbird, or when you are exporting many folders or accounts with filters.
Add-on or profile file, which will you grab
The reassuring truth is that the MBOX you want already exists, Thunderbird has been keeping your folder in exactly that format all along. So there is no conversion to fear and nothing to lose. If you like things tidy, add ImportExportTools NG and use Export folder, and the .mbox lands where you choose. If you would rather not install anything, quit Thunderbird and lift the file straight from the profile. Both give you the same complete mailbox, so the only real question is which you would rather grab, the add-on or the profile file?
