Exactly where and how are you getting this symptom?
The webmail site at »att.yahoo.com/mail
An email client?
A few details would help with the diagnosis (screen shots of your setup and the error messages would be nice).
As far as I know fwmpop.ops.worldnet.att.net is not a valid email server for ATT/Yahoo email.
In fact, it does not even appear to be a valid host name:
DNS request timed out.
timeout was 2 seconds.
*** Request to dcs-gw1.dcs-net.net timed-out
The correct pop3 server does respond to an nslookup:
Aliases: pop.att.yahoo.com, pop-sbc.mail.yahoo.com
Try using these:
POP3: pop.att.yahoo.com, SSL, port 995
SMTP: smtp.att.yahoo.com, SSL, port 465--
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