Unable to send virgin.net email

Last week, suddenly, my sending of emails from my virgin.net address ceased.

Every time I compose an email it immediately goes into the Outbox, and stays there.

I get error message as follows:

The connection to the server has failed.
Subject 'OK?'
Server: 'smtp.virgin.net'
Windows Live Mail Error ID: 0x800CCC0E
Protocol: SMTP
Port: 25
Secure(SSL): No
Socket Error: 10060

Please Help!