I have Windows 7 Home Premium. I can receive emails but I am unable to send any. Has anyone got any suggestions to get my Windows live back. It worked fine till about 2 months ago.

Server Error: 550
Server Response: 550 5.7.3 Requested action aborted; user not authenticated
Server: 'smtp.live.com'
Windows Live Mail Error ID: 0x800CCC78
Protocol: SMTP
Port: 587
Secure(SSL): Yes