How Can We Change Our Outgoing Mail Server Settings?
You select the email account from the list. And click on Change. On the window after changing the Yahoo e-mail settings on your mailing app, click More settings. Click on the Outgoing Server tab and select the My outgoing server requires authentication option. Change the outgoing server port by clicking on the Advanced tab.
Click the "Servers" tab of the Account Properties window. The field under the "Outgoing SMTP Server" heading contains your SMTP server settings.