You can use 3rd party software such as YahooPOPs to get yahoo mail on Outlook or any other email client. Another alternative is the ePrompter software which can download mails from many webmail accounts including yahoo, gmail, rediff, hotmail, etc... But ePrompter wont handle attachments...
if u have yahoo.co.in than u can easily access Yahoo Mail on Outlook Express
but if u have yahoo.com id than u have to use any other 3rd party software as told by sakumar79
I think yahoo is PAID for downloading mails to Outlook.
If we r using free account and try to access mails via outlook using a 3rd party software, we wont b able to access.