I Can't open my Yahoo Mail through Yahoo!Messenger on my laptop.

Hello,
Why can't I open my Yahoo Mail using Yahoo!Messenger on my laptop? The dialogue box says I entered a wrong password. But when I hit "Get a new password" a page appears with the following message: "Unknown Host
Description: Unable to locate the server requested --- the server does not have a DNS entry. Perhaps there is a misspelling in the server name, or the server no longer exists. Double-check the name and try again."