u can create an appl. like outlook thro' Javamail API's.
Complete API's r provided to creat a mail client.
Regarding the pop & smtp  addresses of yahoo & rediff,
actually only paid members get access to pop n smtp addreses frm yahoo or
rediff....
and about hotmail, it doen't use pop n smtp....it uses
http....
just give  a try using following link....put the following link in server  name
option in Outlook, put ur hotmail account n password n check out how it
works....


http://services.msn.com/svcs/hotmail/httpmail.asp


ya one more thing, if u need a readymade mail
client/server, just type "Postcast Mail Server" in google n u'll get a link to
download it free....