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Migrating TB on Windows 10 to MacOS

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  • Last reply by ake867

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I have spent many hours attempting to migrate my Thunderbird 78 email data from a Windows 10 PC to a MacOS PC without success. I have looked at countless articles and have not found one that answers my issue. I have checked the Profile Manager (through the Terminal utility) and my original 6xxxxxxx profile is indicated. The original profile is also shown in the Thunderbird folder copied across from the Windows PC. However, there is another profile indicated that is also shown in the about:profiles folder (in the Application Basics page) and even though my 6xxxxxxx profile is shown as being ‘the profile in use and cannot be deleted’, in the root and local directories the additional new profile is indicated. Clearly I am doing something fundamentally wrong but I am unable to sort it out and require expert advice. Would someone please advise how I can use Thunderbird email on my new PC! Thank you.

Chosen solution

Previously communicated...Possible reason for your problem. If you move your profile between dissimilar operating systems (Windows to Mac OS X for example) the path names in the 'prefs.js' file (your settings) may have the wrong syntax. Rather than manually editing the 'prefs.js' file, try to update the information stored in the prefs.js file by using the "Browse" button for the 'Local directory:' in your Account Settings > Server Settings and Account Settings > Local Folders to specify the correct account and mail directories. Then restart Thunderbird.


Please check the 'prefs.js' - you can open it using a text editor program like Notepad or TextEdit. Carefully look through contents to check for correct entries regarding directories. eg: Windows would have used C:\\Users\\etc Especially check: user_pref("mail.root.imap", "C:\\Users\\User Account\\ etc user_pref("mail.root.none", "C:\\Users\\User Account\\ etc user_pref("mail.root.pop3","C:\\Users\\User Account\\ etc all server number N directories user_pref("mail.server.serverN.directory", "C:\\Users\\User Account\\ etc

The "C:\\Users\\User Account\\ etc "; entries should be pointing to the MAC directories eg: user_pref("mail.root.imap","Macintosh HD\\Users\\<macOsUserName>\\Library\\Thunderbird\\Profiles\\profile name folder\\ImapMail"); user_pref("mail.root.none", "Macintosh HD\\Users\\<macOsUserName>\\Library\\Thunderbird\\Profiles\\profile name folder\\Mail"); user_pref("mail.root.pop3","Macintosh HD\\Users\\<macOsUserName>\\Library\\Thunderbird\\Profiles\\profile name folder\\Mail"); user_pref("mail.server.serverN.directory","Macintosh HD\\Users\\<macOsUserName>\\Library\\Thunderbird\\Profiles\\profile name folder\\Mail\\pop mail account name");

If unsure if correct then post an image showing info in prefs.js file.

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Migration (windows to macOS) :

lets call windows10 computer , P or src. lets call macOS computer , M or dest or dst. TB = Thunderbird.

src & dst must use exact same version of TB.

in dst (macOS) , obtain (exact same verison) TB , install the same version "Thunderbird.app", and then you MUST : DISABLE AUTO-UPDATE option in TB. after that , goto TB main menu > Help > Troubleshooting information > about:profiles > find the line "Default profile: yes" > in that section , find "Root directory" > the last sub-folder in the "Root" dir line, is your current TB's TB-profile sub-folder. write down the sub-folder name please. lets call this sub-folder "new-TB-profile". if you see a button that allows to goto/open the TB-profile location , do that please, to quickly open the TB-profile sub-folder. or else , goto below location in "Finder" manually : "~/Library/Thunderbird/Profiles/<new-TB-profile>/" that is usually here: mac default volume : "/Users/<macOsUserName>/Library/Thunderbird/Profiles/<new-TB-profile>/"

the "~" symbol indicates to your HOME / username directory/folder.

to view the "Library" folder inside your own username / HOME folder in macOS "Finder" , you would have to apply command inside the macOS "Terminal" tool , to unhide/show Hidden files+folders in macOS. in macOS "Finder", goto Preferences > enable "Show all filename extension".

exit from TB.


TB-profile sub-folder actually looks like this : "xxxxxxxx.profile-name" ( each x in xxxxxxxx , is a random alphanumeric characters )


in macOS "Finder" , go one step above or backward of "<new-TB-profile>" sub-folder, that will be here: mac default volume : "/Users/<macOsUserName>/Library/Thunderbird/Profiles/" create a backup sub-folder like below under the "Profiles/" : BAK-<new-TB-profile> go inside "<new-TB-profile>" sub-folder , select all files+folders there : Cmd+A , then copy all selected files+folders list into buffer memory : Cmd+C , then go inside the "BAK-<new-TB-profile>" sub-folder , & move earlier selections : Alt+Cmd+V . so at this point, the "<new-TB-profile>" sub-folder will be empty.


use external storage drive to copy TB-profile from windows computers into mac computers. you may have to use "ExFAT" (extended-FAT) partition in external-drive , as Windows & macOS both recognizes that partition format. external drive cannot be NTFS partition , then macOS will not recognize/read it. external drive cannot be APFS/HFS/HFS+/Ext-Journal partition , then windows will not recognize/read it. ( that is the case generally or by-default . Ofcourse there are 3rd-party apps/tools , which have to be installed separately then those can allow to read various types of partition )


let us assume , in Windows , you have copied windows TB's TB-profile "src-TB-profile" sub-folder , into/inside an external storage drive's "TB" folder , here : "E:\TB\" "E:\TB\<src-TB-profile>\"


plug the external drive in mac.

in macOS "Finder" , select (Cmd+A) all files+folders inside the "<src-TB-profile>" sub-folder , and select "Copy.." (Cmd+C) , & then MOVE (Alt+Cmd+V) into/inside the "<new-TB-profile>" sub-folder.

start TB, all data/settings/emails from src (windows) TB , should be shown to you in (macOS) TB.

when old profile (from Windows) is loaded fine in TB in macOS , Test TB , Restart TB once more , etc, then you can update TB into newer (latest stable) TB version.

Modified by atErik

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On the source computer: copy the contents (not the folder) of the profile folder to a USB or similar drive. Help/Troubleshooting, Profile folder, Open Folder, to open the profile folder. Close TB, copy the contents.

On the target computer: Help/Troubleshooting, Profile Folder, Show in Finder, to open the profile, close TB, delete the contents (not the folder), copy in the contents from the source, delete pkcs11.txt to avoid passwords not being read, restart TB.

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Chosen Solution

Previously communicated...Possible reason for your problem. If you move your profile between dissimilar operating systems (Windows to Mac OS X for example) the path names in the 'prefs.js' file (your settings) may have the wrong syntax. Rather than manually editing the 'prefs.js' file, try to update the information stored in the prefs.js file by using the "Browse" button for the 'Local directory:' in your Account Settings > Server Settings and Account Settings > Local Folders to specify the correct account and mail directories. Then restart Thunderbird.


Please check the 'prefs.js' - you can open it using a text editor program like Notepad or TextEdit. Carefully look through contents to check for correct entries regarding directories. eg: Windows would have used C:\\Users\\etc Especially check: user_pref("mail.root.imap", "C:\\Users\\User Account\\ etc user_pref("mail.root.none", "C:\\Users\\User Account\\ etc user_pref("mail.root.pop3","C:\\Users\\User Account\\ etc all server number N directories user_pref("mail.server.serverN.directory", "C:\\Users\\User Account\\ etc

The "C:\\Users\\User Account\\ etc "; entries should be pointing to the MAC directories eg: user_pref("mail.root.imap","Macintosh HD\\Users\\<macOsUserName>\\Library\\Thunderbird\\Profiles\\profile name folder\\ImapMail"); user_pref("mail.root.none", "Macintosh HD\\Users\\<macOsUserName>\\Library\\Thunderbird\\Profiles\\profile name folder\\Mail"); user_pref("mail.root.pop3","Macintosh HD\\Users\\<macOsUserName>\\Library\\Thunderbird\\Profiles\\profile name folder\\Mail"); user_pref("mail.server.serverN.directory","Macintosh HD\\Users\\<macOsUserName>\\Library\\Thunderbird\\Profiles\\profile name folder\\Mail\\pop mail account name");

If unsure if correct then post an image showing info in prefs.js file.

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Thank you to atErik, Toad-Hall and sfhowes for responding to my query. Unfortunately my Main Bathroom has developed a water leak in an inaccessible place and this is currently causing a big problem and is taking up a lot of my spare time. As soon as the leak is fixed, I will give the migration issue my full attention. Regards, ake867

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Thank you to the three contributors atErik, Toad-Hall and sfhowes. They were surprisingly very different responses but once I had time to look at them I took more from one and a little from the other two and solved the issue fairly quickly. I have to say that I would have thought that there should be a facility in Thunderbird to make the migration easier from Windows to MacOS. Regards, ake867

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