The popular Mozilla Thunderbird mail client bundled with a PortableApps.com launcher as a portable app.
This release updates you to the latest version. It's packaged in PortableApps.com Format so it can easily integrate with the PortableApps.com Suite. And it's Open Source and completely free.
Mozilla Thunderbird is a safe, fast email client that's easy to use. It has many great features, including quick message search, customizable views, support for IMAP/POP, RSS support, and more. Plus, the portable version leaves no personal information behind on the machine you run it on, so you can take your email and address book with you wherever you go.