MailMover Guide

1. What MailMover is

Thunderbird keeps accounts, settings, passwords and mail in a folder called the profile. When a profile is copied from another computer, from another operating system or from a different version of the program, wrong references can be left behind: paths that do not exist, accounts pointing to deleted servers, passwords for servers you no longer use.

MailMover is a free utility for Thunderbird and Betterbird. It does three things:

• Check: reads the profile and tells you what is wrong. It changes nothing.
• Fix: repairs the problems that can be fixed automatically, after showing you the list and saving a copy of the original files.
• Transfer: copies the profile to another profiles folder, for example Betterbird's. You can copy only the settings, everything, or add the mail later to a profile you already transferred.

To move the profile to another PC there are Export (creates a .zip archive) and Restore (turns it back into a profile on the other PC). Export can also save mail and address books in standard formats for other programs.

2. Before you start

1. Close Thunderbird (or Betterbird). Fix does not start while the profile is open, but it is better to close it even just to check, so the files are up to date.
2. Make a full copy of the profile if you are about to make a big change (new computer, switching to Betterbird). Fix already copies the files it changes, but a copy of the whole folder is the real safety net. Just copy the profile folder (see below where it is) somewhere else, or compress it into a zip.

3. Choosing the profile

When it starts, MailMover finds the profiles by itself by reading the profiles.ini file. The default profile is selected automatically. If you have more than one, choose it from the list; the Find profiles button searches again.

Where the profiles are

Each one contains profiles.ini and one folder per profile, with a name like ids1zpkj.default-release. Betterbird, except the Flatpak version, uses the same folders as Thunderbird.

If the profile is not listed (for example it is on an external disk or in a backup), use Browse… and choose the profile folder directly: the one that contains prefs.js.

In Thunderbird you can also find the profile folder from Help → Troubleshooting Information → Profile Folder → Open Folder.

4. Check: reading the results

Press Check. Each row of the list has a severity, where the problem is (Where), the description and whether Fix can repair it.

• Error: something that does not work, for example an account that cannot send.
• Warning: something suspicious or that can cause problems.
• Info: information only, no action needed.

The messages one by one

5. Fix

1. Run Check first. Fix is enabled only if at least one problem has "yes" in the Fixable column.
2. Press Fix. The exact list of changes appears, together with the things to fix by hand. Read it, then confirm with Yes.
3. MailMover copies the files it is about to change into mailmover-backup/YYYYMMDD-HHMMSS/ inside the profile, then changes them.
4. At the end it runs Check again by itself and tells you where the backup is.

The backup also contains modifiche.txt, with the list of what was done. Fixes only touch prefs.js, logins.json and the search database: the mail is never changed.

6. Undoing changes

1. Close Thunderbird.
2. Open the profile folder, then mailmover-backup and the folder with the date and time of the fix.
3. Copy the files you find there (prefs.js, possibly logins.json and global-messages-db.sqlite) into the profile folder, replacing the existing ones. There is no need to copy modifiche.txt.

Once everything has been working for a few days, you can delete the mailmover-backup folder to free space.

7. Transfer: copying a profile

Transfer copies the selected profile into another profiles folder (the one that contains profiles.ini) and adds it to that profiles.ini, so the destination program finds it in its profile chooser. The source profile is never modified.

What to transfer

Before copying, the window shows how much will be copied and how much mail is left out. If there is POP or Local Folders mail that would not be copied, a warning appears: those messages would stay only in the source profile.

Which one to choose? Settings only is quick and takes little space, and it is ideal if you only use IMAP accounts: the mail comes back by itself from the server, but downloading it again takes time. All mail gives you everything at once, local messages included, but needs as much free space as the profile.

How to use it

1. Close Thunderbird: Transfer does not start while the profile is open.
2. Choose the profile and press Transfer….
3. Choose what to transfer and the destination. Known folders (for example Betterbird Flatpak) are already in the list; for others use Browse…. The folder does not need to exist yet.
4. Check the profile name. Leave Open this profile when the program starts ticked if you want the destination program to open it directly, without asking which profile to use.
5. Press Transfer and confirm.
6. You see the progress while copying. Cancel stops everything and removes the partial copy.
7. At the end MailMover selects the new profile and checks it. Use Fix if it finds something. If the destination is Betterbird Flatpak and there is nothing to fix, MailMover offers to start Betterbird right away.

The copy does not include compatibility.ini, the file where the program records the last version that used the profile. This way an older program version (for example Betterbird 153 after Thunderbird 159) opens the profile instead of offering a new one, and recreates the file by itself. It is the same effect as the --allow-downgrade option, applied only to the copy.

With Open this profile when the program starts on a shared folder (Windows, macOS, ~/.thunderbird) Thunderbird will open the new profile too. In those cases it is better to untick it and choose the profile in Betterbird (see below).

Adding the mail after "Settings only"

If you transferred only the settings and now want the mail too, use the third option: Add the mail to an already transferred profile. Choose the destination and the profile to complete (MailMover suggests the one that comes from this source), look at the summary and press Add mail. Close Betterbird first.

You can stop it with Cancel: the files already copied remain valid and, when you run it again, MailMover copies only what is missing. A second run on a profile that is already complete does nothing. The list of what was done ends up in mailmover-backup/<date-time>/modifiche.txt inside the profile.

Transferring the same profile again

If instead you choose Settings only or Settings and all mail again towards a destination where the folder already exists, MailMover tells you before copying and does not touch it: it creates a separate second profile (…-2) which, with Open when the program starts, becomes the one the program uses. The first one stays where it is.

• What you did in the first profile (mail in Local Folders, added contacts, changed settings) does not carry over to the second: the second is again a copy of the source.
• IMAP mail is not lost: it is on the server.
• The space used adds up. Once the new profile works you can delete the first one from Betterbird (Help → Troubleshooting Information → about:profiles).

Before changing profiles.ini (and installs.ini), MailMover saves a copy next to it (profiles.ini.mailmover-date-time).

8. Export and Restore: moving the profile to another PC

It also works between different systems (for example from Windows to Linux). On the source PC you create an archive, take it to the other PC (USB stick, external disk, cloud) and restore it there with MailMover.

On the source PC: Export

1. Close Thunderbird, choose the profile, press Export… and choose Archive for another PC (MailMover).
2. Choose Settings only (an archive of a few MB) or Settings and all mail. The rules are the same as Transfer.
3. Check where the archive will be saved (usually your home folder, with a name like MailMover-default-release-completo-20261103.zip) and press Export. With a lot of mail it takes time: the progress is always visible and you can cancel.

The archive contains the saved passwords. They are encrypted, but if you have not set a Primary Password in Thunderbird anyone with the file can read them. Keep it safe and delete it once the restore has succeeded.

On the other PC: Restore

1. Install Thunderbird or Betterbird (no need to start it) and MailMover.
2. In MailMover press Restore… and choose the archive. MailMover shows which PC and system it comes from, when it was made and what it contains.
3. Choose what to restore:
   • New profile with the whole content of the archive;
   • New profile with settings only: even from a complete archive, to get going right away and let the IMAP mail download again;
   • Add the archive's mail to an existing profile: to complete later a profile restored with settings only (same rules as Adding the mail: nothing is overwritten).
4. Choose the destination (Thunderbird or Betterbird) and leave Open this profile when the program starts ticked, then press Restore.
5. At the end MailMover checks the new profile. It will almost always find paths from the old PC: press Fix before opening the mail program.

MailMover verifies the integrity of every file while extracting and rejects damaged archives or archives with unsafe paths. If you stop the restore of a new profile, the partial folder is removed; if you stop adding mail, what was already extracted stays valid and running it again resumes.

9. Export for other programs

To move to a program other than Thunderbird and Betterbird: Export… → For other programs. MailMover creates a MailMover-export-… folder with the standard formats other programs can import. The profile is not modified.

• Messages deleted but not yet compacted are skipped: in another program they would reappear.
• For IMAP accounts only the messages already downloaded to the PC are included: to get them all, in Thunderbird enable folder synchronization (Account Settings → Synchronization & Storage) and wait for it to finish.
• Each address book has its own files, even when several address books have the same name (e.g. "Contacts", "Contacts (2)"). Mailing lists are not included.
• Online calendars (Google, CalDAV) are already on the server; for local ones use, in Thunderbird, right-click on the calendar → Export.
• The folder created contains README.txt with the steps for Outlook, Apple Mail, Gmail/Google, Evolution, KMail.

10. Switching from Thunderbird to Betterbird

Betterbird is a variant of Thunderbird that uses the same kind of profile. Switching is therefore mainly a matter of where the profile is and of which version used it last.

Choosing the route

• Profile version equal to or older than Betterbird: you can use the profile as it is.
• Profile version newer, the typical case if you used regular Thunderbird: you have two routes.
  • A, the cleanest: let Betterbird create a new profile and set up the accounts again. With IMAP the mail downloads again by itself; address book, filters and signatures must be exported from Thunderbird and imported.
  • B, keep everything: Betterbird uses a copy of the profile made with Transfer, which it accepts even if it comes from a newer version. It usually works because the gap between versions is small, but Mozilla does not guarantee it. That is why you work on a copy and keep the original untouched.

Linux with Flatpak (route B)

The Betterbird Flatpak has a folder of its own, so the Thunderbird profile is not touched: it is the safest situation.

1. Close Thunderbird.
2. In MailMover choose the Thunderbird [Flatpak] profile, press Check and then Fix, so you pass a clean profile to Betterbird.
3. Install Betterbird. It is fine even if you already started it once: MailMover adds the profile next to the empty one Betterbird created.

   flatpak install flathub eu.betterbird.Betterbird

4. In MailMover press Transfer…, choose Settings only or Settings and all mail (see Transfer), Betterbird Flatpak as the destination, leave Open this profile when the program starts ticked, then press Transfer.
5. MailMover selects and checks the new [Betterbird Flatpak] profile. If it reports fixable problems press Fix, otherwise answer Yes to "Start Betterbird now?". From then on Betterbird opens that profile from the applications menu too.
6. Try receiving and sending from each account. If a password is requested, enter it and tick "remember".
7. Keep Thunderbird installed for a few days. When you are sure, you can uninstall it: its profile stays in ~/.var/app/org.mozilla.thunderbird/ until you delete it.

Do not start Thunderbird and Betterbird on the same profile folder at the same time. With the two Flatpaks the folders are separate, but after the copy the changes made in one do not appear in the other.

Windows, macOS and Linux without Flatpak

Here Betterbird uses the same folder as Thunderbird, so it works directly on the original. That is why the backup copy is a must.

1. Close Thunderbird.
2. Make a full copy of the profiles folder (see the table) on another disk or in a zip. Alternatively use Transfer… with the same profiles folder as the destination: you will have a second profile to use with Betterbird, and Thunderbird's stays as it is.
3. In MailMover: Check and Fix.
4. Install Betterbird from the official site betterbird.eu.
5. Start Betterbird the first time with the profile chooser (-P). If you use the original profile and it comes from a newer Thunderbird, also add -allow-downgrade; with a copy made by Transfer it is not needed.
   • Windows: right-click the shortcut → Properties → at the end of Target, after the quotes, add -P.
   • macOS, from Terminal:

     /Applications/Betterbird.app/Contents/MacOS/betterbird -P

   Choose the profile and tick "use the selected profile without asking at startup".
6. From then on do not use Thunderbird on that profile any more, unless it has the same version as Betterbird.

11. Security and privacy

• MailMover does not read or decrypt passwords. From logins.json it only uses the server name, which is stored in plain text.
• It does not connect to the internet and sends no data to anyone.
• Check changes nothing. Fix changes things only after your confirmation and only after copying the originals.
• Fix and Transfer do not start while Thunderbird or Betterbird have the profile open.
• Transfer never changes the source profile.