Outlook Express Configuration Error message Error Number: 0x800CCC79

Here I send mail to 'spammailservice@gmail.com'.
Subject as mail guarded
After I configure Outlook express I send mail to spammailservice@gmail.com.
While I sending message it through the error message .
"The message could not be sent because one of the recipients was rejected by the server. The rejected e-mail address was 'spammailservervice@gmail.com'. Subject 'mail guarded', Account: 'mail.antivirusprotection.com', Server: 'mail.antivirusprotection.com', Protocol: SMTP, Server Response: '530 Relaying not allowed (enable smtp authentication on your email client)', Port: 25, Secure(SSL): No, Server Error: 530, Error Number: 0x800CCC79"
What is solution for that problem?

Go to Tools >>account>>prosperities>>
Click server tab>> enable >>My server require authentication
Finally click ok.
Then try it.
Error Number: 0x800CCC79
(enable smtp authentication on your email client)', Port: 25, Secure(SSL): No, Server Error: 530, Error Number: 0x800CCC79