The message could not be sent. The setting for your outgoing email [SMTP] server might need to be configured. To find the server settings for '*** Email address is removed for privacy ***', please contact your email service provider.

Subject  
Server Error: 550
Server Response: 550 Authentication required. Help at http://www.earthlink.net/go/emailsettings
Server: 'smtp.earthlink.net'
Windows Live Mail Error ID: 0x800CCC79
Protocol: SMTP
Port: 25
Secure(SSL): No

How can this be fixed?