Yahoo POP3 and SMTP Settings:
Find below the basic POP3 settings that you need to configure in the email program where you want to access Yahoo mails.
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. firstname.lastname@example.org)
Password: Your Yahoo! Mail password
Read more: http://techblissonline.com/yahoo-pop3-and-smtp-settings/#ixzz1CKFD6Su8
Looks like you've got the wrong port for your outgoing mail - Use 465 instead.
In response to your comment: Updated the content.
Looking at the wording, have you tried that port without authentication, or the efault port with authentication. The optional seems to suggest one or the other.