Move your Profile To A Network Drive
Install Thunderbird separately on each computer but store your profile on a network file share. To launch This method to sync Thunderbird email requires that you have access to a shared / network drive. This is the most convenient method in the long run. However, it involves moving your existing profile to that drive, which can be tricky.
First make sure Show hidden files and folders is on. Close Thunderbird. Now copy the profile folder to the desired location on the network drive.
In Win7 you will find your Thunderbird profile under > C:\Users\<Windows user name>\AppData\Roaming\Thunderbird\Profiles\
If you do not see the “AppData” folder, that’s because it’s hidden. Make sure Show hidden files and folders is on.
Once the profile has arrived in its new location, go to > “C:\Users\<Windows user name>\AppData\Roaming\Thunderbird\” and open the profiles.ini file in a text editor.
This file lists all profiles registered with your installed Thunderbird. Locate the one you just moved and change the > Path= line to the new location, for example > Path=”E:\Thunderbird Profile\xxxxxxx.default”. Make sure to change > IsRelative=1 to > IsRelative=0 in case you switch from a relative to a non-relative path. Also, the direction of slashes in the path will change from “/” (relative) to “\” (non-relative).
Make this change to the profiles.ini file on each computer Thunderbird is installed on. Once all machines are working correctly clean up the profiles on the C: drives by deleting the xxxxxxx.default file.
The only drawback I see to this method is there might be some issues if T-Bird is running on multiple machines and more than one machine tries to check and update mail at the same time. I have not tested this so I'm not sure of the effects of data collision.
A Mozilla Help article is here
http://kb.mozillazine.org/Synchronizing_mail_on_two_computers_(Thunderbird)