It supports upgrades by installing right over an existing copy, preserving all your email and settings. Thunderbird, Portable Edition is packaged in a Installer so it will automatically detect an existing installation when your drive is plugged in. Plus, the portable version leaves no personal information behind on the machine you run it on, so you can take your email and adress book with you wherever you go.

It has lots of great features including quick message search, customizable views, support for IMAP/POP, RSS support and more.

Thunderbird is the safe, fast email client that's easy to use. Update automatically or install from the portable app store in the Platform. Mozilla®, Thunderbird® and the Thunderbird logo are registered trademarks of the Mozilla Foundation and are used under license. And it's open source and completely free. It's packaged in Format so it can easily integrate with the Platform. It's the popular Thunderbird email client bundled with a launcher as a portable app.

A new version of Thunderbird, Portable Edition has been released.

Mozilla thunderbird portable