Here's an idea, though I haven't tried it myself yet. At
you can get a portable version of Thunderbird, which will run under
Windows (98 and above) and also run under Linux if the Wine libraries
are installed. If you're lucky, and those extensions will run under
Wine as well, you can work the same way in both operating systems.

If you want to pursue this, PortableApps have their own web forums,
where you can ask someone with more experience about this.

Rick Carter