Moving your profile folder - Thunderbird
From MozillaZine Knowledge Base
Thunderbird doesn't store your data in the program directory. It stores it in a "profile" directory instead in order to make it easier to upgrade or re-install without worrying about losing your data. Your profile has all of your mail, address books, settings, saved passwords, add-ons etc. Help -> Troubleshooting Information -> Show Folder (Open Containing Folder in older versions) will open your profile directory using windows explorer (or its equivalent if you are not using Windows). That is the easiest way to find where your profile is stored.
Thunderbird doesn't discover profiles by looking in the default location where profiles are stored, instead it uses the profiles.ini file to find what profiles exist and where they are stored. While its possible to copy your profile somewhere and then edit that file to point to the profile its easy to make a mistake doing that. Its recommended that you use a little known feature of the profile manager to move the profile instead.
You can move a profile anywhere you want except the program directory. Normally its moved to use a more convenient location or to restore a backed up profile. If you want to move a profile to a different PC see Move to a new PC instead if you're using Windows.
Use the Profile Manager to move your profile
These instructions will seem strange since there is no "move profile" or "register profile" button in the profile manager but it isn't a mistake. When you press the "Create Profile" button and then browse to your profiles location it does not do anything to your profile, it merely updates profiles.ini to point to that profile so that Thunderbird can find and use that profile. You could do the same thing by editing profiles.ini yourself but it is very easy to make a mistake doing that.
Create a new profile and copy the old one over it
You could also copy the profile over an existing profile instead. If you do that delete its contents first.
Modify profiles.ini to point to the new location
Sharing a profile with another user
If you want to share a profile with another user on the same PC (who has their own account) the easiest solution is to copy the profile to a location that doesn't depend upon a user name such as c:\profiles, and then have each user "move it" using the profile manager. That will update each users profiles.ini.
1. Can't launch the profile manager
Thunderbird isn't added to the path, so you need to specify the path when typing Thunderbird -profilemanager at Start -> Run. For example, "C:\Program Files\Mozilla Thunderbird\Thunderbird" if you're using XP. The double quotes are necessary due to the embedded space in Program Files. If you omit it Windows will think you want to run C:\programs. The exact path depends upon what operating system you are using and whether you customized the location the program was installed.
One of the easiest ways to get the right command line if you're using Windows is to copy the contents of the Target: edit field in the shortcut used to run Thunderbird, and then append -P to it. Windows supports both -P and -profilemanager command line arguments, Linux and OS X only support -profilemanager.
If you're running XP you'd typically want:
If you're running Windows 7 you'd typically want:
If you have problems with the double quotes another solution would be to open a console window in the Thunderbird program directory from Windows Explorer and then type Thunderbird -P
You can do that under Vista and Windows 7 by navigating to the Thunderbird program directory in Windows Explorer, holding down the Shift key while right clicking, and selecting Open Command Prompt Here from the context menu. If you're running an older version of Windows and don't want to find something like XP's "Open Command Window Here" Power Toy to add that feature run Windows Explorer, navigate to the Thunderbird program directory, press ALT+D to go to the location bar (which shows the current directory) at the top of the window and then type cmd in the location bar. That will create a console window whose default directory is the Thunderbird program directory. 
2. Thunderbird can't find the profile
Thunderbird is extremely finicky about the contents of profiles.ini. If things go wrong and you didn't use the recommended solution sometimes the best solution is to exit Thunderbird and delete the profiles.ini file. Then run Thunderbird and immediately exit (don't fill out anything in the account wizard). That will create a new good profiles.ini file that points to a profile that is just a stub. Then find the location of the stub profile in the profiles.ini file and copy the contents of the profile you want to move to that directory. Don't copy the profile directory, just copy its contents.
3. Copied the profile directory
Another common mistake when copying the profile over an existing profile is to copy the entire profile directory, not just the contents. Thunderbird doesn't discover a profile by looking in the Profiles directory. It looks in profiles.ini to find where they are. When it looks at the location it found in profiles.ini it expects to find prefs.js and several others files there. If you copied the profile directory there it won't find those files (because they are in a child directory), so it will assume the profile doesn't exist.