All my efforts to access my yahoo (and gmail) accounts in all major mail client like Evolution and Thunderbird failed until i came across little known mail client stuff called zimbra. It is based on Mozilla Prism technology and said to be a next generation mail client. I have Installed it in my laptop recently. I found it much faster, and lighter than Evolution. It also comes with all other stuffs like calender and others which major mail client has to offer.
Important point is, you need not have to worry about incoming / outgoing server (particullarly for yahoo), port number and bhla bhla things... simply login by giving your username and password thats it...
Here is the link to download Yohoo Zimbra Desktop which is of 50Mb.
Read this page before installing and configuring Yahoo Zimbra Desktop.
Once you downloaded YahooZimbra right click on it ---> Properties ---> click Permission tab ---> enable Allow executing file as a program then close it.
Now double click on the modified downloaded file ---> click Run in terminal tab and follow the simple instruction here after...