Yahoo email account has to be configured to enable POP 3 access, only then the account details can be used to access email through Microsoft Outlook or some other POP 3 email clients. To configure yahoo email, logon to yahoo mail account and click on the Options link
Click on the POP Access and Forwarding Options link available in the options screen.
This should display the options to configure Web and POP access. Select the options as displayed below.
To view your yahoo account POP settings, click on the View POP settings link. These details are required in order to configure your account in Mail Clients like Microsoft Outlook.