1. Open your email client program.
2. Select Tools
3. Select Accounts
4. Highlight Your Email Account
5. Select Properties on right
6. Locate the email account settings for your particular client.
7. Change the POP server to pop.att.yahoo.com.
8. Change the SMTP server to smtp.att.yahoo.com.
9. Select Advanced Tab
10. Check the option labeled Use an encrypted connection (SSL) and change the SMTP port to 465.
11. Check the option labeled Use an encrypted connection (SSL) and change the POP3 port to 995.
12. Confirm the above settings then click OK.