Exporting email messages

I am going to be installing Ubuntu LNR on my AA1 and assume that I will lose all my Aspire One Mail stored emails in the process. Can I get hold of my stored email messages (including archived emails) and export them, say, as text files for future reference?

I have been using Aspire One Mail successfully for around two years, so have quite a few stored emails, and forwarding them all to myself would be quite time consuming. I have been deleting each message from the server automatically upon downloading.

Matthew