Written by Jennifer Walsh. Reviewed for technical accuracy by Shubham Dixit, Independent Expert in Email Forensics and Data File Conversion. Updated 22 October 2026.
Shubham is an independent external reviewer and not an employee of PCDOTS.
Quick summary. Windows 10 Mail can’t import mail files, so you move Thunderbird email in through an account instead. Add an IMAP account in Thunderbird, drag your local messages into an IMAP folder so they upload to the server, then add that same account in Windows 10 Mail and it syncs the mail down. No software needed, and your folders ride along.
On this page
- How do you transfer Thunderbird emails to Windows 10 Mail?
- Why Windows 10 Mail won’t import your Thunderbird files
- How to move Thunderbird emails to Windows 10 Mail free
- Should you switch to the new Outlook instead?
- How to keep a local Outlook copy with a converter
- Which route fits you?
- Frequently asked questions
How do you transfer Thunderbird emails to Windows 10 Mail?
You transfer Thunderbird emails to Windows 10 Mail through an email account, not a file. Windows 10 Mail reads accounts over IMAP, so the trick is getting your Thunderbird mail onto an IMAP server that Windows 10 Mail can then sync.
That one fact changes everything you read elsewhere. Windows 10 Mail has no Import button for MBOX, EML or PST, so dragging a file in won’t work. Upload the mail to an IMAP account instead and Windows 10 Mail pulls it down for free.
Here’s why the file route is a dead end, the free IMAP method step by step, a heads-up about the new Outlook and the point where a converter helps if you want a local copy.
Dragging an MBOX file into Windows 10 Mail goes nowhere, uploading the mail to an IMAP server lets Windows 10 Mail sync it down.
“The mistake I see is people hunting for an import button in Windows 10 Mail that was never there. Mail isn’t a file reader, it’s an account client, so you feed it an account. Put the Thunderbird mail on an IMAP server, add that account to Mail and it appears. I lean on IMAP because the folders and attachments survive the trip. When someone also wants a copy sitting on the disk, that’s when a converter to PST or EML makes sense, not for the Mail app itself.” Shubham Dixit, Data File reviewer (draft, pending approval)
Why Windows 10 Mail won’t import your Thunderbird files
Thunderbird keeps your mail on the disk as MBOX files inside your profile folder. Windows 10 Mail works a different way. Microsoft’s Mail app connects to accounts over IMAP, POP or Exchange and shows what the server holds.
So Windows 10 Mail has nowhere to load an MBOX or EML file, no Import option at all. Knowing that up front saves you hunting for a button that was never built. Mail needs the messages on a server, and the free method below puts them there.
How to move Thunderbird emails to Windows 10 Mail free
You push the Thunderbird mail up to an IMAP account, then add that account in Windows 10 Mail. Both apps read the same server, so the mail lands in Windows 10 Mail with nothing bought.
Here are the five steps.
- In Thunderbird, add a free IMAP account if you don’t already have one, like Outlook.com or Gmail.
- Make a new folder under that IMAP account in the folder list.
- Open your Local Folders, select the Thunderbird messages and drag them into the IMAP folder. Thunderbird uploads them to the server.
- Open Windows 10 Mail, select Add account and sign in to the same IMAP account.
- Windows 10 Mail syncs the folder down, and your Thunderbird mail shows there.
Big mailbox? Upload it in smaller batches so the server accepts it cleanly. Send yourself a test first, move one folder and confirm it appears in Windows 10 Mail before you move the rest.
The free route in five beats, drag Local Folders mail onto an IMAP folder to upload it, then add that account in Windows 10 Mail and it syncs down.
Should you switch to the new Outlook instead?
Worth knowing before you settle in. Microsoft is retiring the Windows Mail app and moving people to the new Outlook for Windows, so Mail won’t be around forever.
Same IMAP account works in the new Outlook, so you can add it there and skip the move later. For a Thunderbird archive you want to open in Outlook, a PST or EML copy drops straight in, which the next section covers.
How to keep a local Outlook copy with a converter
IMAP gets the mail into Windows 10 Mail, yet it lives on the server, not your disk. For a copy you hold yourself, or an archive for Outlook, convert the Thunderbird MBOX to a file format Outlook opens.
PCDOTS Thunderbird Converter reads the Thunderbird profile on Windows and saves it to PST, EML, PDF or MSG, which classic Outlook and the new Outlook open. Remember Windows 10 Mail still can’t load those files, so the converter is for Outlook and backups, while the free IMAP route above is the way into Mail itself.
Which route fits you?
Match your goal to the method. Here’s the quick version.
| Method | Best for | Good to know |
|---|---|---|
| IMAP upload | Mail into Windows 10 Mail | Free, folders and attachments ride along |
| New Outlook account | A client that lasts | Free, same IMAP account, Mail is retiring |
| Thunderbird Converter | A local Outlook copy | Saves PST or EML, not for Mail |
Key takeaways
- Windows 10 Mail can’t import MBOX, EML or PST, so you move mail through an account.
- Transfer Thunderbird emails to Windows 10 Mail free by uploading them to an IMAP account.
- Microsoft is retiring Windows Mail, so adding the account in the new Outlook is smarter long term.
- For a local copy, a converter saves Thunderbird mail as PST or EML for Outlook.
Frequently asked questions
Can Windows 10 Mail import MBOX or EML files?
No. Windows 10 Mail connects accounts over IMAP, POP or Exchange and has no file import. Move the mail through an IMAP account and Windows 10 Mail syncs it down.
How do I move Thunderbird email to Windows 10 Mail for free?
Add an IMAP account in Thunderbird, drag your local messages into an IMAP folder so they upload, then add that account in Windows 10 Mail so it syncs the mail.
Where does Thunderbird store my emails?
Thunderbird keeps mail as MBOX files in your profile, under AppData\Roaming\Thunderbird\Profiles on Windows. That’s the data you upload or convert.
Is Windows 10 Mail going away?
Yes. Microsoft is moving people to the new Outlook for Windows. Your IMAP account works there too, so you can add it in the new Outlook and skip a second move.
How do I keep a local PST or EML copy of Thunderbird mail?
A converter saves the Thunderbird MBOX to PST or EML, which classic Outlook and the new Outlook open. Windows 10 Mail still can’t load those files.
Will my folders and attachments stay intact?
Yes. Over IMAP the folder you upload keeps its structure and attachments, and a converter keeps them too when it writes PST or EML.
Getting your Thunderbird mail into Windows, the honest way
Moving Thunderbird emails to Windows 10 Mail comes down to one truth, Mail reads accounts, not files. Upload your mail to an IMAP account and Windows 10 Mail syncs it for free, folders and all. Since Microsoft is retiring Mail, adding the same account in the new Outlook saves you a repeat move, and a converter gives you a PST or EML copy for Outlook when you want one on the disk. Move one folder first and check it lands, then bring the rest across.
