Webmail Woes...

I used my personal Yahoo email account for testing a Biztalk orchestration
which sent emails through the SMTP adapter.  While debugging some
connectivity issues, I opened Outlook Express on the dev box (which is
running in an image) and configured it to access my Yahoo mail account in
order to verify that I had the correct settings.

A while later I returned to Outlook Express and discovered that it downloaded
the entire content of my mailbox from Yahoo to the dev server box, and cleared
all the messages off of the server. So now the only copy of all my mail from the
last 18 months is in Outlook Express on a friggin dev image :(

Does anyone know how to transfer those messages back to Yahoo
mail?   Does GMail support any import capabilites?  As a last
resort I might import them into Outlook but I would really prefer to have them
available online.