YPOPs! (previously known as YahooPOPs!) is an open-source application that provides POP3 and SMTP access to Yahoo! Mail. It is available on the Windows, Linux, Solaris and Mac platforms. The project was started by Anuj Seth in 2002 and is now supported by a larger community of developers.
Yahoo! Mail disabled free access to its POP3 service on 24th April, 2002. This application emulates a POP3 server and enables popular email clients like Outlook, Netscape, Eudora, Mozilla, etc., to download email from Yahoo! accounts. We do not go against the license agreements of Yahoo! Mail. This application is completely legitimate and well within the realms of legal software.
YPOPs! is more like a gateway. It provides a POP3 server interface at one end to talk to email clients and an HTTP client (browser) interface at the other which allows it to talk to Yahoo!