I have Windows Live2009 and I have not been able to send out emails for a few weeks. Everything was working fine until then. I contact my internet provider Comcast and spent a great deal of time with them on the phone and they suggested the error was with the software and to contact you. Below is the message I received today when trying to send a test email:

The message could not be sent because the server rejected the sender's e-mail address. The sender's e-mail address was 'mo**********@comcast.net'.

Subject 'test'
Server Error: 550
Server Response: 550 5.1.0 Authentication required
Server: 'smtp.comcast.net'
Windows Live Mail Error ID: 0x800CCC78
Protocol: SMTP
Port: 587
Secure(SSL): Yes

Original title: Cannot send email out using Windows live email