""Here are the basic server settings for Yahoo! Mail:
Incoming Mail (POP3) Server: pop.mail.yahoo.co.uk
Outgoing Mail (SMTP) Server: smtp.mail.yahoo.co.uk (use authentication,
optionally use port 587)
Account Name/Login Name: Your Yahoo! Mail ID (your email address without the
"@yahoo.com")
Email Address: Your Yahoo! Mail address (e.g. user@...)
Password: Your Yahoo! Mail password

If you can't add new POP or SMTP servers, you'll need to change your current
server settings to access your Yahoo! Mail account. Write down your current
settings first—you might need to revert to them later if you decide to send and
receive messages from your other email addresses.""

You also need to employ 'authentication'.