Do you have "My server requires authentication" checked?
Your ISP has an illustration of the correct settings:
http://www.btopenworld.com/faqs/manual_email_setup
Gary VanderMolen
"DaN" <DaN@discussions.microsoft.com> wrote in message news:468E7442-1465-4F2F-96FA-A55A1809812F@microsoft.com...
> The message could not be sent. The authentication setting might not be
> correct for your outgoing e-mail [SMTP] server. For help solving this
> problem, go to Help, search for "Troubleshoot Windows Mail", and read the
> "I'm having problems sending e-mail" section. If you need help determining
> the proper server settings, please contact your e-mail service provider.
>
> The rejected e-mail address was 'danielward@btinternet.com'. Subject 'Re:
> Dell Desktop Purchase ', Account: 'mail.btinternet.com', Server:
> 'mail.btinternet.com', Protocol: SMTP, Server Response: '530 authentication
> required - for help go to
> http://help.yahoo.com/help/us/mail/pop/pop-11.html', Port: 25, Secure(SSL):
> No, Server Error: 530, Error Number: 0x800CCC78