Unable to send mails from windows live mail app, all the mails sending is moved to outbox folder

error:

Your server has unexpectedly terminated the connection. Possible causes for this include server problems, network problems, or a long period of inactivity.

Subject 'Fw: Shirley and Marcy'
Server: 'outbound.att.net'
Windows Live Mail Error ID: 0x800CCC0F
Protocol: SMTP
Port: 465
Secure(SSL): Yes

System configuration: windows 7 Home Premium