Nish, have you looked at the C# code sample on YDN?
http://developer.yahoo.com/mail/code/
You'll need to set up the CookieContainer property of the ymws object with a new
System.Net.CookieContainer. Then populate the container with the cookies you get
back from BBAuth.
The code sample linked above explains this in pretty good detail/
--
Ryan Kennedy
Technical Yahoo!
rckenned@...