That is an excellent question and yes it is easily done.
Open an email that is addressed to the account you wish to forward. from with in that email click on the Message
tab and select Create Rules From Message
. Make sure the eight check box in the first windows is checked "Where the message is from a specific Account".
In the second windows select "Forward to people". In the third window click on the "people" link and enter the Yahoo account you wish it forwarded to. It is that easy.
When creating a rule you can select as many option as you wish.
The only down side is if your computer loose power or the Outlook Express program is some how turned off you will not receive your email. I use message rules to receive my email on the road also, but I am seldom gone for more than 36 hrs. With that said it is a great tool.
Here is a Microsoft article
you may fine relevent.