How do I backup my email so that I can import it all back in at a later time if I need to?

[mark Pyles]

Hi everyone:

I'm using Ubuntu 8.04 (Gnome desktop) with thunderbird 2.0.0.19. Is 
there a way to backup all  my mail and folders to be able to import them 
back into thunderbird at a later time if needed say like to do a 
re-install or if the computer runs a muck? Thanks.

Mark