Yahoo mail has a feature using which you can forward mails receive in Yahoo account to another email address. This settings is available as part of the Yahoo Account Options. To enable automatic forwarding of Yahoo Mail, click the Options menu (available at the top right hand corner) and select Settings from the list of available menus.
In the Settings screen, navigate to Accounts tab and click Edit button in the Yahoo account section.
In the popup window, navigate to Access your Yahoo Mail elsewhere section and select Forward radio option.
You have an option to specify whether you want to retain a copy of emails received in your account or mark as read or Forward only.
Click the Save Changes button to confirm and save the changes. This feature is helpful when you have multiple email accounts and you want to use receive all your emails in one account.