There are a lot of articles and videos circulating about how to set up Yahoo! POP3 email accounts in Outlook 2007, Mozilla Thunderbird, Outlook Express, etc. Yahoo! requires users to pay for a premium subscription to have POP3 access. Most of these proposed solutions are a bit dated as of the time of this writing, and almost all of them involve changing your regional or location settings to Yahoo! Asia. None of these seem to work any more; my settings didn't even have Yahoo! Asia as an option. Besides, who wants to pay to have Yahoo! email offline on your computer when it is free on the Yahoo! Mail web site, and even on your mobile phone?
Maybe Yahoo! has grown wise to the situation by now, or the 2011 Google issues with China has, let's say, "adjusted" the Internet relationship between the United States and China (a large part of Asia). Whatever the case may be, in the Northeastethern US, changing any of the POP3 settings in the Yahoo! Mail web interface hasn't worked.
The good news is that Outlook 2007 supports IMAP as well as POP3 email setups. This article provides an alternate way to set up Yahoo! within Outlook 2007 that does work. It involves using IMAP mail settings, instead of POP3. IMAP synchronizes content with the server better anyway... » More...