CANT SEND MAIL

NEED HELP PLEASE , THIS IS MY PROBLEM:

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 'r.jimenez@kkinternationallogistics.com'.
Subject 'Re: EXPO- EDS -TIN8370', Account:
'mail.kkinternationallogistics.com', Server:
'mail.kkinternationallogistics.com', Protocol: SMTP, Server Response: '451
Blocked - see http://www.spamcop.net/bl.shtml?216.171.88.67', Port: 25,
Secure(SSL): No, Server Error: 451, Error Number: 0x800CCC79