Can't send mails from windows mail

My Windows Mail has sunddenly stopped sending. I am recieving mail OK but can't send. I get the following error message:

Account: 'mail.btinternet.com', Server: 'mail.btinternet.com', Protocol: SMTP, Server Response: '451 See http://pobox.com/~djb/docs/smtplf.html.', Port: 587, Secure(SSL): No, Server Error: 451, Error Number: 0x800CCC6A

Any ideas?

The code message, 0x800ccc6a due to the SMTP processing error. Check for mail account setup may be due to multiple mail account setup is present and you trying to work with account that currently not connected also check here http://forums.techarena.in/windows-v...ail/794852.htm

Thanks, as I said, Googlemail is working Ok but my other email address with BTinternet [a UK provider] is the one that has failed, they have both worked OK in the past. Perhaps I need to contact BT.

Jon

Have you tried by reinstalling BT? get a newer version and reinstall it.