The only major worry you might have is misplacing the USB drive if it's got most of your e-mails on.If there was some way to protect users from this kind of accident, then Thunderbird Portable would be the perfect portable app. In terms of performance, there are few noticeable differences between Thunderbird Portable and it's big brother.It's really easy to install although we found synchronization with the mail exchange could sometimes be troublesome.

The e-mail client is one of Thunderbird Portable's most useful features - you can take your e-mail with you wherever you go although obviously, you can quickly fill up a flash drive with e-mails as you download them.Fortunately, Thunderbird Portable itself only takes 30-40MB of space. Thunderbird Portable can run from a USB stick and leaves no hard disk footprint meaning you can use it with ease anytime, anywhere. If you're always on the move and a big Thunderbird fan, then this program should answer a lot of your prayers. Redesigned version of Thunderbird that you can take with you

Thunderbird mail app