Portable Thunderbird OS X is the popular Mozilla Thunderbird email client packaged as portable application so you can take your email, address book and account settings with you.
From the experience of Portable Firefox OS X, here is the popular Mozilla Thunderbird email client packaged so you can carry around with you on any portable device, USB thumb drive, iPod, portable hard drive, memory card, other portable device (also on your internal hard disk) as long as it has 60 MB of free space and use on any Mac OS X computer, taking your email, address book and account settings with you.