How to Enable Yahoo's SSL
Many email providers offer Secure Sockets Layer, or SSL, support. SSL is a form of Internet security that encrypts all email transmissions between your computer and the mail server. If you have a Yahoo Mail account, you can configure SSL through the Microsoft Outlook application. Once you have enabled SSL, outgoing and incoming messages will be encrypted.
Launch the Microsoft Outlook program on your computer.
Go to "Tools" in the top menubar and select "Email Accounts."
Select the "View or change an existing account" radio button and click "Next."
Highlight your Yahoo Mail account from the list and click "Change."
Go to the "Advanced" tab at the top of the window.
Place check marks next to "This server requires an encrypted connection (SSL)" in both the incoming and outgoing server sections.
Change the incoming port number to "995" and the outgoing port to "465."
Click "OK" and "Finish" to save the settings and enable SSL.