I have a hotmail account but I mostly use the Gmail interface. I have never had issues in the past setting up my hotmail account on Gmail through SMTP. Today however, I keep getting this error message:

Authentication failed. Please check your username/password.  [Server response: 535 5.2.1 Login to your account via a web browser to verify your account. code(535) ]

I can log in to my hotmail account on hotmail just fine. I tried changing the password but that didn't fix anything. What gives?