I used Windows Essentials 2012 for my email accounts.  Starting this morning, I got the following error message when I tried to send messages.  The messages weren't sent. 

An unknown error has occurred.

Server: 'smtp.gmail.com'
Windows Live Mail Error ID: 0x8007007A
Protocol: SMTP
Port: 465
Secure(SSL): Yes

Any idea what might be causing this?