entourage and me email authentication issue

Hi Everyone, before someone mentions it, I know I need to upgrade my software, but for right now this is what I am working with, and I kind of get by with it for now. Anywho, I recently updated my e-mail to a @me.com address. When I added the account into my Entourage I had no problem authenticating, and I receive mail with no problem. Untill today when I went to forward a message using my (outdated) MacBook Pro, instead of my iPhone, I received an error message explaining that Entourage does not support any of the available authentication methods.

In a nutshell, I have no idea what that means and what to do. Please help by telling me how to fix this, or how to obtain the new software without spending a fortune to take care of the issue altogether 🙂

thanks everyone!