Mobility Email is a portable open-source distribution of Mozilla's Thunderbird. It can be used on a desktop computer as a normal e-mail application, or it can run directly from a USB key (like the iPod Shuffle) without needing to be installed on a computer.

Mobility Email is based on technology from PortableThunderbird with Enigmail/GPG, which in turn is based on Portable Thunderbird. Mobility Email has more features than the standard Mozilla Thunderbird e-mail client and has several extensions pre-loaded to allow you to access your Hotmail, Yahoo! and Lycos e-mail accounts, and to view your contacts. It also uses the Enigmail OpenPGP extension and GnuPG to provide OpenPGP signing and encryption.

Read more about the Mobility Email email client at http://www.biosmagazine.co.uk/article.php?id=2284.