Configure Outlook 2007 for your Yahoo address:

1. Enable POP in your email account. Don't forget to click Save Changes when you're done.
2. Open Outlook.
3. Click the Tools menu, and select Account Settings...
4. On the E-mail tab, click New...
5. If you are prompted to Choose E-mail Service, select Microsoft Exchange, POP3, IMAP, or HTTP, and click Next.
6. Fill in all necessary fields to include the following information:

Your Name: Enter your name as you would like it to appear in the From: field of outgoing messages.
Email Address: Enter your full Yahoo email address (username@yahoo.com).
Password: Enter your email password

Incoming mail server settings

• POP server: plus.pop.mail.yahoo.com
• Use SSL
• Port: 995

Outgoing mail server (SMTP) settings

• SMTP server: plus.smtp.mail.yahoo.com
• Use SSL
• Port: 465
• Use authentication
• Account Name/Login Name: Your Yahoo! Mail ID (your email address without the "@yahoo.com", for example, “testing80”)
• Email Address: Your Yahoo! Mail address (for example, testing80@yahoo.com)
• Password: Your Yahoo! Mail password

Troubleshooting tips
If you still can’t send Yahoo! Mail from your mail program, you may be accessing the Internet through an ISP that is blocking the SMTP port. If this is the case, try setting the SMTP port number to 587 when sending email via Yahoo!'s SMTP server.
Your email program gives you the option of either deleting your Yahoo! messages from the Yahoo! server after downloading them into your mail reader, or leaving them on the Yahoo! server so you can see them online in your Yahoo! account, too.

Congratulations! You're done configuring your client to send and retrieve Yahoomail messages.