Migrate Thunderbird to Another Computer

Thunderbird stores every account, folder and message inside one profile folder that sits deep in Windows and cannot be dragged to a new PC like a document. A failed copy gives you an empty inbox and years of mail stuck on an old drive. Below are three ways to bring Thunderbird to a new PC, with Mozilla's official steps, limits and fixes for missing mail.

What do you need before you shift Thunderbird to a new PC?

You need a USB drive or other transfer device, Thunderbird installed on your new PC and matching versions on both PCs. Mozilla says both versions of Thunderbird should be up to date or identical before a transfer, since a mismatch can make it fail. Close Thunderbird before you bring Thunderbird to a new PC, because open files copy badly.

Thunderbird's folder is hidden on Windows so show hidden files in File Explorer first. Mozilla's official Guide to move Thunderbird data to a new computer lists identical steps for Windows, Mac and Linux.

How to shift Thunderbird to a new PC by copying your profile?

Copy your Thunderbird profile folder from your old PC to your new PC and replace what is there. That retains accounts, folders and messages in one move. It is a free way to shift Thunderbird to a new PC when versions match.

Steps on your old computer

1. Connect your USB drive.
2. Open Thunderbird, go to Help and select Troubleshooting Information.
3. Find Profile Folder entry and select Open Folder.
4. Quit Thunderbird.
5. Go up folder levels until you reach your Thunderbird profile folder. On Windows it sits at C:\Users\your-name\AppData\Roaming\Thunderbird.
6. Copy that Thunderbird profile folder to your USB drive.

Steps on your new computer

1. Install Thunderbird, open it and close account setup window.
2. Go to Help, then Troubleshooting Information and select Open Folder beside Profile Folder.
3. Quit Thunderbird.
4. Go up to your Roaming folder and paste your copied Thunderbird profile folder.
5. Select Replace when Windows asks about existing data, then open Thunderbird.

On a Mac, Mozilla says to copy your Thunderbird profile folder from your Library folder or share it with AirDrop. Mozilla also notes that copying your folder doubles as a backup. If your profile sits on a remote drive through Profile Manager, create a new profile on your new PC and point it to that location instead.

How to transfer Thunderbird emails to another computer with MBOX files?

Save folders as MBOX files to transfer Thunderbird emails to another computer, then import them into Thunderbird. That suits cases when your old Thunderbird no longer opens or when you want only some folders. Thunderbird stores local mail in MBOX style files so one file contains one folder of messages.

1. On your old PC, export your folders to MBOX files. See how to Export MBOX from Thunderbird for steps.
2. Copy your MBOX files to a USB drive and then to your new PC.
3. Install Thunderbird on your new PC and import your MBOX files. See how to Import MBOX to Thunderbird account for steps.
4. Check folder counts against your old Thunderbird to confirm your Thunderbird emails reached your new computer.

Already have an MBOX backup and no working Thunderbird? Corbett's MBOX Converter opens MBOX files without a mail client.

Steps to bring Thunderbird to a new PC with software

1. Install Corbett Thunderbird Migrator on your Windows PC and start setup with Run as Administrator.
2. Select Open, then Desktop Email Clients and Thunderbird. Software lists every profile and account on your PC.
3. Preview your folders and messages. Untick Junk and Trash for a clean start.
4. Set date, sender, subject or attachment filters if you want fewer emails.
5. Select Export and choose a target. Options are a live mailbox on your new setup or MBOX, PST, EML or PDF files for your new PC.
6. Sign in to your target account. Microsoft 365 and Google Workspace open their own sign-in page and Gmail takes an app password.
7. Start migration and check your new mailbox when it ends.

Software that moves your mail copies mail from a profile on disk so your old Thunderbird remains untouched. Corbett's page says copied profiles from an old PC work too, which suits cases when your old PC no longer starts. Calendar, tasks, mail rules, passwords and add-ons do not carry over. Test on one profile in free demo, then buy. Lifetime licence starts at $99 with a 30-day money-back window. For a file copy only, see Thunderbird backup software. For contacts, see how to Export Thunderbird contacts to CSV.

Which way to shift Thunderbird to a new PC is best?

Copy your profile for a full move between matching versions. Use MBOX files when only some folders need to move. Use software to shift Thunderbird to a new PC when versions differ, folders are large or you need a Gmail or Microsoft 365 target.

Why are Thunderbird emails missing on your new computer?

Missing mail comes from five causes when you bring Thunderbird to a new PC. Thunderbird was open during your copy. You pasted your folder one level too deep or too high. Hidden files stayed hidden so you copied nothing. Thunderbird versions differ. Your IMAP account kept only message headers on disk so folders look empty.

For IMAP accounts, open Thunderbird's Synchronization and Storage settings, enable the option to store messages on your computer and wait for downloads to finish before you copy. Corbett's page lists an identical fix. To save files from messages after your move, see how to Download attachments from Thunderbird or how to Extract email addresses from Thunderbird.

Questions about Thunderbird on a new PC