Split from this thread.

I am all of  a sudden unable to send email as well.  Please advise.

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 '<Unknown>', please contact your email service provider.

Subject 'Representation'
Server Error: 555
Server Response: 555 5.5.2 Syntax error. z71sm4575042qkz.16 - gsmtp
Server: 'smtp.gmail.com'
Windows Live Mail Error ID: 0x800CCC79
Protocol: SMTP
Port: 587
Secure(SSL): Yes