Thunderbird supports running from removable drives with minimal reconfiguration. To make life even easier, I've repackaged Thunderbird as a complete, removable drive-friendly email client.

Now you can check your pop3 account everywhere you travel.

Installation / Use
To install, just download the ZIP and unzip it to the root directory of your USB drive. It will create a "thunderbird" directory and all the requisite directories underneath. To use Thunderbird on your drive, launch it with the PortableThunderbird.exe file in the thunderbird directory. DO NOT launch the thunderbird.exe file directly, as this will create a profile on your hard drive.

Upgrading
To upgrade to a newer version of Portable Thunderbird, simply backup your existing Portable Thunderbird folder (/thunderbird/ on down). Download the latest version. Then copy your profile directory from the old version to the new version. That's all there is to it.