not all usa users can use pop3 for yahoo yet.

[sanjay]

I have 2 yahoo mail accounts.  One started in 1997 the other in 2003.
Both are free yahoo mail accounts.  On the 1997 account I am able to
use pop3 with no problems.  On the 2003 account I am not allowed to
use pop3.  So I have no idea what yahoo is doing, but it is clear that
not all USA users are allowed to use pop3 yet.