If you are moving from one operating system to another (such as changing from Windows to Mac or Linux) then you must manually move your profile from one computer to the next. You'll need to first back up your profile, then follow the directions for "Restoring to a different location."

Backing up a profile

To back up your profile, first close Thunderbird if it is open and then copy the profile folder to another location.

1. Shut down Thunderbird.
2. Locate your profile folder, as explained above.
3. Go to one level above your profile's folder, i.e. to %APPDATA%\Mozilla\Thunderbird\Profiles\~/Library/Thunderbird/Profiles/~/.mozilla/Thunderbird/
4. Right-clickHold down the Ctrl key while you click on your profile folder (e.g. xxxxxxxx.default), and select Copy.
5. Right-clickHold down the Ctrl key while you click the backup location (e.g. a USB-stick or a blank CD-RW disc), and select Paste item.

Restoring a profile backup

1. Shut down Thunderbird.
2. If your existing profile folder and profile backup folder have the same name, simply replace the existing profile folder with the profile backup, then start Thunderbird.
   
   Important: The profile folder names must match exactly for this to work, including the random string of 8 characters. If the names do not match or if you are restoring a backup to a different location, follow the steps below.

Restoring to a different location

If the profile folder names do not match or if you want to move or restore a profile to a different location, do the following:

1. Completely close Thunderbird, as explained above.
2. Use the Thunderbird Profile Manager to create a new profile in your desired location, then exit the Profile Manager.
   
   Note: If you just installed Thunderbird on a new computer, you can use the default profile that is automatically created when you first run Thunderbird, instead of creating a new profile.
3. Locate the backed up profile folder on your hard drive or backup medium (e.g., your USB-stick).
4. Open the profile folder backup (e.g., the xxxxxxxx.default backup).
5. Copy the entire contents of the profile folder backup, such as the mimeTypes.rdf file, prefs.js file, bookmarkbackups folder, etc.
6. Locate and open the new profile folder as explained above and then close Thunderbird (if open).
7. Paste the contents of the backed up profile folder into the new profile folder, overwriting existing files of the same name.
8. Start Thunderbird.

Moving a profile

Occasionally, you might want to move a profile or tell Thunderbird to use a profile stored in another location.

1. Shut down Thunderbird.
2. Move the profile folder to the desired location. For example, on Windows XP, move the profile from C:\Documents and Settings\[username]\Application Data\Thunderbird\Profiles\xxxxxxxx.default to D:\Stuff\MyMailProfile. (If you are reverting to a backed up profile, this step isn't necessary. Just note the current location of the profile you want to restore.)
3. Open up the profiles.ini file in a text editor. The file is located in the application data folder for Thunderbird:
   • On Windows 7/Vista/XP/2000, the path is %AppData%\Thunderbird\
   • On Windows 95/98/Me, the path is usually C:\WINDOWS\Application Data\Thunderbird\
   • On Linux, the path is ~/.thunderbird/
   • On Mac OS X, the path is ~/Library/Thunderbird/
4. In the profiles.ini file, locate the entry for the profile you've just moved. Change the Path= line to the new location.
5. If you switch from a relative path to a non-relative path, the direction of the slashes may need to change. For example, in Windows, non-relative paths use backslashes, whereas relative ones use forward slashes. Change IsRelative=1 to IsRelative=0.
6. Save profiles.ini and restart Thunderbird.