my email worked fine till a couple of days ago, now I keep getting this error message

Unable to send or receive messages for the Optusnet.com (d.a.rose) (1) account. Your server has unexpectedly terminated the connection. Possible causes for this include server problems, network problems or a long period of inactivity.

Server: 'mail.optusnet.com.au'
Windows Live Mail Error ID: 0x800CCC0F
Protocol: POP3
Port: 110
Secure(SSL): No

Any help would be appreciated.

many thanks