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MoveMyInbox

Guide

Export mail from Thunderbird

Good news: Thunderbird already keeps each folder as an MBOX file on your disk. There’s nothing to export, you just need to find the files and make sure they are complete.

Step 1: Make sure all your mail is on this computer

For POP3 and Local Folders, your messages are already stored locally. For IMAP accounts (Gmail, Outlook.com, iCloud, most company mail), Thunderbird may only keep message headers locally, so check this first:

  1. Open Settings → Account Settings (on older versions Tools → Account Settings, or the ☰ menu → Account Settings).
  2. Select Synchronization & Storage under the IMAP account.
  3. Tick Keep messages for this account on this computer. Click Advanced… to choose which folders are synced, and make sure no “don’t download messages larger than” limit is set if you want everything.
  4. Wait for Thunderbird to finish downloading (watch the status bar). To force a single folder, right-click it → Properties → Synchronization → Download Now.

Step 2: Compact your folders (recommended)

When you delete a message, Thunderbird only marks it as deleted inside the MBOX file until the folder is compacted. Compacting removes those leftovers so they don’t reappear in Outlook. Use File → Compact Folders (or right-click an account → Compact).

Step 3: Find your profile folder

  1. Open Help → Troubleshooting Information (press Alt on Windows if the menu bar is hidden).
  2. In the table, next to Profile Folder, click Open Folder (Show in Finder on a Mac).
  3. Inside the profile you’ll see Mail (POP3 accounts and Local Folders) and ImapMail (IMAP accounts), with one subfolder per account, for example ImapMail/imap.gmail.com.

To find one specific account’s folder, open Account Settings → Server Settings for that account; the Local Directory field at the bottom shows its exact path.

Typical profile locations:

  • Windows: %APPDATA%\Thunderbird\Profiles\xxxxxxxx.default-release
  • macOS: ~/Library/Thunderbird/Profiles/xxxxxxxx.default-release
  • Linux: ~/.thunderbird/xxxxxxxx.default-release (or ~/snap/thunderbird/common/.thunderbird for the Snap package)

What the files are

FileWhat it is
Inbox, Sent, Archives… (no extension)The mailboxes themselves, in MBOX format. These are what we convert.
Inbox.msf, Sent.msf…Thunderbird’s index (summary) files. Not needed; we skip them automatically.
Inbox.sbd/A directory holding the subfolders of Inbox, again as extension-less MBOX files.
filterlog.html, msgFilterRules.dat, popstate.datSettings and logs. Skipped automatically.

Using Maildir storage?

If an account’s folders are directories full of individual message files (cur, new, tmp), it uses Maildir (“file per message”) storage instead of MBOX. Install the free ImportExportTools NG add-on, then right-click each folder → ImportExportTools NG → Export folder and choose the MBOX format. Upload the resulting files.

Step 4: Convert to PST

  1. Close Thunderbird so the files aren’t being written to while you upload them.
  2. In MoveMyInbox, start a New conversion.
  3. Drag the account folder (for example ImapMail/imap.example.com) onto the upload area, or click Choose a folder. We walk through the folder, pick up every mailbox and ignore the index files. You can also select individual mailbox files.
  4. Leave Folders on One folder per mbox file, so Inbox, Sent and your own folders each become an Outlook folder of the same name.
  5. Upload, pay if needed, and download your PST.

Tip

Thunderbird’s Trash and Junk mailboxes are converted too. Remove them from the list before uploading if you don’t want them.

Next step

Once you have the PST, see how to import it into Outlook.

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