Mozilla's Thunderbird is a popular e-mail client known for its stability and ease of use. While there are many applications available to help with the transferring of your Thunderbird data to another computer, it is just as easy to perform the actions manually. All Mozilla applications store the entirety of your data and personal settings in a profile folder on your computer. By simply transferring this folder to a new machine, you can quickly and easily restore your previous e-mail settings.
Download and install a copy of Thunderbird on what will be the destination computer. Run the application after installation so that it can create a default profile for you to replace. Close down Thunderbird on both the original and destination computer.
Open your file manager on the original computer and navigate to the Thunderbird profile directory. In Microsoft Windows Vista and 7, this is stored in the C:\users[Your User Name]\Application Data\Thunderbird\Profiles\ directory. Under Microsoft Windows XP, there will be a "Documents and Settings" folder before the "Users" folder.
Locate the default profile on your original computer. This will have a string of numbers followed by ".default". Copy all of the files in this directory to a USB pen drive or over the network to the destination computer. Make sure to copy only the files in the directory and not the folder itself.
Copy the files from the original default folder into the destination computer's default folder. Launch Thunderbird on the destination computer and your e-mail and personal settings will automatically be added to your new copy of Thunderbird.
This profile-copying trick works with all Mozilla applications. You can copy your Firefox settings using this technique as well.