Outgoing mail failure

I have recently set up windows mail and incoming mail is fine but I keep
getting a failure notification for outgoing mail. Help anyone? I have tried
using 587 for the outgoing port but to no avail.

Your server has unexpectedly terminated the connection. Possible causes for
this include server problems, network problems, or a long period of
inactivity. Subject 'test', Account: 'pop.tiscali.co.uk', Server:
'smtp.tiscali.co.uk', Protocol: SMTP, Port: 25, Secure(SSL): No, Socket
Error: 10053, Error Number: 0x800CCC0F
Janie B