web.config:

    <system.net>
        <mailSettings>
            <smtp deliveryMethod="Network" from="testuser@domail.com">
                <network defaultCredentials="true" host="localhost" port="25" userName="kaushal" password="testPassword"/>
            </smtp>
        </mailSettings>
    </system.net>



code:

    protected void btnSubmit_Click(object sender, EventArgs e)
    {
        var to = "contact@thepowercoder.com";
        var from = txtEmail.Text;
        var mailFrom = new MailAddress(from);
        var mailTo = new MailAddress(to);
        var message = new MailMessage(mailFrom, mailTo);

        message.Subject = string.Format("New Message From Contact Me Page, {0}", from);
        message.Body = txtMessage.Text;
        message.IsBodyHtml = true;

        var client = new SmtpClient();
        client.Send(message);
    }