You can simply use the POP3 service available to premium users ($19 per year I believe). If you are such a user, you simply need to retrieve your Emails with pop.mail.yahoo.com & send them via smtp.mail.yahoo.com & you can use them with any Email client such as Outlook, Outlook Express, Eudora, Pegasus, Thunderbird, etc.
I have noticed that the POP3 service seems to be available free of charge for people with a yahoo.fr Email (such as me). I still have no idea why they would make such a service free for some people & not for others.
