Using Windows Live mail I am unable to send or forward emails of only a modest size . I can however receive such mails

Alao I receive the following message "

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

Server: 'mail.btinternet.com'

Windows Live Mail Error ID: 0x800CCC0F

Protocol: POP3

Port: 110

Secure(SSL): No

This problem has arisen since changing my ISP and email address.