I'm going to mix some of the coolest possibility given by thunderbird.
1) You can put thunderbird into a usb drive, so that you can use it in any pc with connection and usb, having your mails always with you
2) You can use the same mail folder for two different installations of thunderbird, a linux and a windows one
So: we can install thunderbird on our zaurus, and set the mail folder on the sd card, in a fat partition. Then we can put a windiws installation of thunderbird in that partition, setting the mail folder the same we use for zaurus thunderbird installation.
Doing so, we can RECEIVE and READ equally our mails with the zaurus or with any windows pc with usb port without duplicates, without fragmented mailbox and so on.
Drawbacks:
1) thunderbird on zaurus isn't that fast (at all)
2) we'll use some MB of our sd card for the windows installation
last point: it should be possible also pen-drive installation of thunderbird for linux. So, we can have 3 different clients (linux x86, win32 x86, linux zaurus) collecting mails in the same folder, in any possible condition of internet connection, without the need of drivers or syn software.
Isn't it a good idea?