Corbett

Thunderbird Migrator

Corbett Thunderbird Migrator moves Mozilla Thunderbird mail into Gmail, Google Workspace, Microsoft 365, Outlook.com or a company IMAP server, folders and attachments intact. It can also write PST, MBOX or PDF files for a new PC. Windows software that finds every profile by itself.

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4.8 out of 5 from 112 reviews

Mail travels from this computer's profile folder to the new mailbox, and Corbett never holds or sees it.

Free demo, scanned clean on VirusTotal and a 30-day money-back window.

Lifetime licence from $99 Free trial saves 10 emails per folder

What moves

Thunderbird Migrator for Folders and Accounts

Leaving Thunderbird for a work Microsoft 365 mailbox, moving the family to Gmail or retiring an old PC all hit one wall. Years of mail sit in local MBOX files that no webmail can open. Thunderbird Migrator uploads those folders to the new account and leaves the profile as it was.

Carried over

Folder tree
Attachments
Inline images
Signatures
Message dates
Read/unread status
Full headers

Thunderbird folders

Inbox
Sent
Drafts
Archives
Templates
Junk
Local Folders

Destinations

Gmail
Google Workspace
Microsoft 365
Outlook.com
Yahoo Mail
Zoho Mail
Any IMAP host
PST file

Not carried

Calendar and tasks
Mail rules
Account passwords
Add-ons

Thunderbird's own export only feeds Thunderbird

Tools, then Export in Thunderbird packs the profile into a ZIP that only another Thunderbird can import. Gmail and Microsoft 365 cannot read it. Thunderbird Migrator takes those same folders and uploads them to the new mailbox.

Thunderbird to another computer

Core features

Thunderbird Migrator, Screen by Screen

Profile found, folders ticked, mail landing in the new inbox. Every Thunderbird Migrator stage below is a real wizard screen.

Source

Add Thunderbird and the Target Account

Open, Desktop Email Clients, Thunderbird lists every profile and account on the PC. Then add the destination. A Microsoft 365 or Google Workspace account opens its own sign-in page, while Gmail and other IMAP hosts take an app password.

Default profile paths filled in
Copied profiles from an old PC accepted
Sign-in window for 365 and Workspace
Stopped uploads restart from the last message

Thunderbird folder tree with selection checkboxes

Folder selection

Choose Thunderbird Folders to Migrate

Thunderbird Migrator lists accounts and folders in a branching view with message counts. Leave Junk and Trash unticked and the new mailbox starts clean.

Account, folder and subfolder checkboxes
Totals listed next to folder names
Local Folders included
Junk and Trash easy to skip

Message preview

Check Thunderbird Messages Before Upload

Open any message in the profile first. Thunderbird Migrator adds a reading pane and four analysis tabs to confirm the right folders are going over.

Content shows body, sender, recipients and subject the way Thunderbird stored them
Message header traces the delivery path of every message
Properties gives size, flags and attachment list
Hex and raw message display the stored MBOX source

Selective backup

Migrate Thunderbird Mail Selectively

Folder and message searches work on their own. Thunderbird Migrator can upload only the last five years, only one client's mail or one project folder and leave the rest in Thunderbird.

Upload a date range only
Match sender, recipient or subject
Messages with attachments only
Leave out oversized mail
No second copy on a rerun
Attachments saved apart on request

Output options

Upload Thunderbird Mail or Write New Files

Upload to a live mailbox, or write files for a PC that will run Outlook. Many switchers do both, a PST for the archive shelf and a working copy in the new inbox.

Gmail, Google Workspace, Microsoft 365, Outlook.com or Zoho
PST, MBOX, EML or PDF files for a new computer
Mail from servers rather than Thunderbird goes through the IMAP Migration Tool
Need a file copy only? Use the Thunderbird Backup Tool instead

Before uploading

Thunderbird Migrator Account Prep

Thunderbird Migrator takes mail off the disk, but the new mailbox needs a working login. Sort these out first.

Gmail target

Make a Google app password

Google wants 2-Step Verification on before it issues an app password. Create one under App passwords and enter that 16 letter code as the Gmail password here.

Work mailbox

Microsoft 365 signs in on its own page

Business mailboxes send their own Microsoft or Google login window with MFA. Thunderbird Migrator keeps only the access token it hands back.

IMAP accounts in Thunderbird

Download full messages first

An IMAP account in Thunderbird may hold only headers on disk. Under Synchronization and Storage, keep messages on this computer, wait for the download, then migrate.

Setup help for new accounts inside Thunderbird is in Add Gmail to Thunderbird and Add Hotmail to Thunderbird.

Free demo

Try Thunderbird Migrator on a Sample

Install the Thunderbird Migrator demo, point it at the profile and upload 10 emails from every folder to the new account. Check them there before paying.

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Before purchase

Drag and Drop vs Thunderbird Migrator

The free route is adding the new Gmail or Microsoft 365 account inside Thunderbird and dragging folders across. For a few small folders that is fine. Big folders often stall halfway and a retry leaves duplicates. Here is the side by side.

Task	Drag and drop	Thunderbird Migrator
Cost	Free	$99 one time
A few small folders	Works fine	Works too, extras below
Large folders	Stalls or times out on big copies	Resumes after a dropped link
Filter by date or sender	Full folders only	Date, sender, subject and size filters
Where mail goes	Accounts set up in Thunderbird	Gmail, 365, Outlook.com, IMAP or PST
Unattended runs	Thunderbird must stay open	Runs with Thunderbird closed
Many profiles	One profile at a time	All profiles in one session
File copy	None	PST, MBOX, EML or PDF in the same run

Green rows mark where dragging folders in Thunderbird is enough.

For a handful of small folders, dragging them into a new IMAP account inside Thunderbird costs nothing. Setting up Gmail there is explained in Add Gmail to Thunderbird .

Specifications

Thunderbird Migrator PC Specs

Download details

Released: Dec 2020
Download size: 87.4 MB
Trial limit: 10 emails per folder
Delivery: Download link and key by email
Licence: Lifetime, up to 5 machines

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System

Hard disk: 150 MB to install, plus room for output
RAM: 4 GB minimum
Processor: 1 GHz, 2.4 GHz advised
Rights: Run as Administrator
Thunderbird: Profile on this PC or a copied one

Supported editions

Windows 11, 10, 8 and 7 in 32-bit or 64-bit, plus Windows Server 2008 to 2025.

No macOS or Linux build.

Corbett has built Windows email utilities since 2020. Questions about Thunderbird Migrator reach the developers who wrote it.

Working process

Thunderbird Migrator Video

Rather follow stills? The IMAP backup guide pictures every wizard screen in order.

Common questions

Thunderbird Migrator FAQs

Profiles, targets, duplicates and what the migration leaves alone.

How do I migrate Thunderbird to Microsoft 365?

Open the tool, choose Thunderbird under Desktop Email Clients and tick the folders. Select Microsoft 365 as the target and complete Microsoft's sign-in. Folders appear in Outlook under their original names.

Will Thunderbird folders work in Gmail?

Yes. Select Gmail, enter your address and a Google app password and start. Every Thunderbird folder turns into a Gmail label.

Do I need Thunderbird installed?

No. A profile folder copied from an old computer is enough. Browse to the copy, the folder that contains prefs.js, and your accounts load.

Are Local Folders migrated?

Yes. Local Folders and POP account mail upload like IMAP folders. Most buyers come to the tool for exactly this, since dragging cannot reach them easily.

Will my folder structure survive?

Yes. Subfolders keep their nesting in the target. Gmail shows them as nested labels and Outlook as folders.

Can I move Thunderbird to a new computer with Outlook?

Yes. Save your profile as a PST file, carry it over and open it in Outlook with File, Open and Export.

Can I migrate several Thunderbird profiles?

Yes. Every profile on your PC is listed and every one can go to its own target account.

What about Thunderbird contacts?

Your address book can be saved as a CSV file and imported into Gmail or Outlook contacts. Email addresses inside messages can be extracted too.

Is my Thunderbird profile changed?

No. Thunderbird Migrator only reads it. Uninstall Thunderbird yourself once the new account looks complete.

Can I upload newer mail later?

Yes. Run again with a start date after your first pass and duplicate skipping on. There is no ongoing sync.

How big a profile can it handle?

Not in the full version. Upload speed depends on the target server, and Gmail and Microsoft 365 both throttle big imports, so a 20 GB profile can take hours.

What do I need for an IMAP server target?

The server name, port, your email address and password. Most hosts use port 993 with SSL.

Does my mail pass through Corbett?

No. Uploads go from your PC to your mail provider. Corbett stores nothing.

Can a Mac profile be migrated?

Yes, from Windows. Copy your Mac or Linux profile to a Windows PC and migrate from there, since the tool has no Mac build.

What does the Thunderbird Migrator demo do?

It uploads 10 emails from every folder with preview and filters unlocked, so you can check the result in your new mailbox.

Step by step

Thunderbird Migration Guides

Reading for the work around a Thunderbird switch.

To cloud mail

To Outlook

Into Thunderbird

Every mail source we move is listed on the Email Migration Tool page. Server mailboxes go through the IMAP Migration Tool. Loose MBOX files are handled by the email converter tool. Restoring saved mail to a server is a job for the email recovery software. To read MBOX files without exporting, use the free email viewer software. Related pages: Thunderbird Backup Tool and Gmail Migration Tool. Also see the Yahoo Mail Migration Tool, Gmail backup tool, Outlook.com backup tool, AOL backup tool and Webmail backup tool.

User testimonials

Thunderbird Migrator Reviews

Ratings from 112 people who moved Thunderbird profiles with Corbett.

4.8 out of 5

Collected across 112 reviews from software sites and support email. Both quotes below are copied exactly.

Large IMAP move, patient support

I had a large amount of data to migrate from Thunderbird to IMAP server, and I connected with their support executive Nick. He was patient and helpful in completing the entire process.

Jack H. Pankratz

Install error fixed fast

I initially had an installation error and connected with one of their support executives who helped me resolve it. The best part of the Thunderbird Migrator is that they provide quick assistance at any time of the day.

Dean J. Sliva

Get started

Leave Thunderbird Without Losing a Folder

Get the demo, aim it at a Thunderbird profile and upload a sample from every folder. A lifetime licence is $99 with a 30-day refund window.

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87.4 MB · Windows 11 to 7 and Windows Server 2025 to 2008 · 30 day money back