Mail sending failure

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C#3.0

C#

Hi everyone,
This is the code where im trying to send mail. Since one n half month im trying to send mail, but its giving very much trobule. Few told have to configure in web.config file. I dint know anything, but some how i made changes.

<system.net>
        <mailSettings>
            <smtp>
                <network host="localhost" port="25"/>
            </smtp>
        </mailSettings>
    </system.net>

Tell me if any one knows why v have to make changes in config file,

Some one told have to configure smtp... but im not sending from local server. My website already hosted...

my website url is www.karthavyaebusiness.com

Message.From = new MailAddress("http://mail.karthavyaebusiness.com");
Message.To.Add(new MailAddress("kriish05@yahoo.com"));
Message.Subject = "Enquiery About Product";
Message.Body = "Testing Message";
SmtpClient client = new SmtpClient("127.0.0.1");
client.Send(Message);

Pls help me any one, Im stranges to .net.
Advance thnks to all...