Do you get this after failing to send?
Your server has unexpectedly terminated the connection. Possible causes for this include server problems, network problems, or a long period of inactivity. Account: 'pop.wanadoo.co.uk', Server: 'smtp.wanadoo.co.uk', Protocol: SMTP, Port: 25, Secure(SSL): No, Socket Error: 10054, Error Number: 0x800CCC0F