尝试提交基本表单时出现SMTP问题

我很抱歉收到这么多代码，但我的表单有问题。我已经尝试了各种方法来配置它，但根本无法发送。它所需要做的就是发送一封带有消息正文的电子邮件，但每次我点击提交时，它只会显示错误（来自catch块）。

这是在C#ASP.NET中。

我是新开发的，如果有任何帮助，我将不胜感激。提前感谢！

protected void submitButton_Click(object sender, EventArgs e)
{
    if (Page.IsValid)
    {
        string messageBody = "//numerous textboxes, dropdown lists, and checkboxes";
        SmtpClient smtp = new SmtpClient();
        MailMessage message = new MailMessage();
        message.IsBodyHtml = false;
        try
        {
            // Prepare to and from e-mail addresses
            MailAddress fromAddress = new MailAddress("info@kellersflowers.com");                
            MailAddress toAddress = new MailAddress(emailTextBox.Text);
            message.From = fromAddress;
            message.To.Add(toAddress);
            message.Subject = "Contact Form Email";
            message.Body = messageBody;
            // Server details
            smtp.Host = "email.goidp.com";
            // Credentials
            smtp.UseDefaultCredentials = true;
            // Send the email
            smtp.Send(message);                
            // Inform the user
            noticeLabel.Visible = true;
            noticeLabel.Attributes.CssStyle.Add("display", "block");
            //noticeLabel.Text = "E-mail sent";
            noticeLabel.Text = "Thank you, we have received your information and will be in touch soon.";
            // and clear the form
            fullNameTextBox.Text = String.Empty;
            companyTextBox.Text = String.Empty;
                 //many others, this is just to give the idea;
        }
        catch (Exception ex)
        {
            errorLabel.Text = "Error sending e-mail:<br/>'n" + ex.Message;
            Response.Redirect("estimate-error.html?error=1");
            errorLabel.Visible = true;
            errorLabel.Attributes.CssStyle.Add("display", "block");
            errorLabel.Text = "Error sending e-mail:<br/>'n" + ex.Message;
        }
    }
    else
    {
        //errorLabel.Text = "Error sending e-mail. Check required fields<br/>";
        //Response.Redirect("estimate-error.html?error=2");
        errorLabel.Visible = true;
        errorLabel.Attributes.CssStyle.Add("display", "block");
        errorLabel.Text = "Error sending e-mail. Check required fields<br/>";
    }
}

我是这个网站的新手，所以如果我需要发布更多信息，我会的。非常感谢。

smtp.Credentials = new System.Net.NetworkCredential("info@kellersflowers.com", "PasswordForEmail");