How do I move old emails from one an old email account to a new one?

I changed servers ( from sbcglobal.net ) and want to move all my old emails to yahoo.com, any suggestions?How do I move old emails from one an old email account to a new one?
I think the only thing you can do is re-send your e-mails to your new e-mail account - I don't think there is a system where you can swap e-mails to different addresses.



Hope this was some help =].