Go to Site administration > Server > Email > Outgoing mail configuration
To get the SMTP servers functioning, only four values need to be set:
SMTP hosts: smtp.mail.yahoo.com:465
SMTP security: SSL
SMTP username: Your full Yahoo email address.
SMTP password: Your Yahoo mail password
These settings work with most desktop, mobile, and web email programs and services. After you set up Yahoo Mail in your preferred email client, the mail and your Yahoo folders appear in both locations: in Yahoo and in your preferred app or web interface, such as Gmail.