Sende e-mail fra et skema

Jeg har et simpel skema, der skal sende e-mail, når skemaet sendes. Både til den, som udfylder det og til et andet forudbestemt e-mail adresse. Efter at jeg har lagt det på driftserver virker det kun for mig. Andre får ikke nogen e-mail sendt.
Jeg bruger ASP.NET 2.0.

Her er mit skema (codeBehind):
------------------------------
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Net.Mail;
using System.ComponentModel;
using System.Web.SessionState;
using System.IO;
using System.Text;
using System.Web.Caching;
using System.Web.Compilation;

public partial class kontaktform : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
Response.CacheControl = "no-cache";
DateTime nu = DateTime.Now;
lblDato.Text = nu.ToShortDateString();
}
protected void btnSend_Click(object sender, EventArgs e)
{
Page.Validate();
if (Page.IsValid)
{
try
{
//create the mail message
MailMessage myMail = new MailMessage();
if (Upload1.HasFile)
myMail.Attachments.Add(new Attachment(Upload1.PostedFile.InputStream, Upload1.FileName));
if (Upload2.HasFile)
myMail.Attachments.Add(new Attachment(Upload2.PostedFile.InputStream, Upload2.FileName));
//set the addresses
myMail.From = new MailAddress(System.Configuration.ConfigurationManager.AppSettings["FROM"]);
myMail.To.Add(txtEmail.Text);
myMail.CC.Add("aaa@etellerandet.dk");
myMail.CC.Add("bbb@etellerandet.dk");
myMail.BodyEncoding = System.Text.Encoding.UTF8;
myMail.SubjectEncoding = System.Text.Encoding.UTF8;
myMail.IsBodyHtml = false;
//set the content
myMail.Subject = "MitEmne";
myMail.Body = "Tak for ...: " + "\n\n" +
"Navn? " + txtBox1.Text + "\n" +
"Nummer? " + txtBox2.Text + "\n" +
"Eventuelt billede 1: " + Upload1.FileName + "\n" +
"Eventuelt billede 2: " + Upload2.FileName + "\n" +
"Kommer du? " + radioKontakt.SelectedItem.Text + "\n\n" +
"Med venlig hilsen" + "\n";
SmtpClient smtp = new SmtpClient(System.Configuration.ConfigurationManager.AppSettings["SMTP"]);
smtp.Send(myMail);
}
catch (NullReferenceException ex)
{
lblFejl.Text = ex.ToString();
}
finally
{
Response.Redirect("bekraeftelse.aspx", false);
}
} return;
}
}
---------

Og her er min web.Config:
-------------------------
<?xml version="1.0"?>
<configuration>
<appSettings>
<add key="SMTP" value="etellerandet.aaa.dk" />
<add key="FROM" value="noreply@etellerandet.dk" />
</appSettings>
<connectionStrings/>
<system.web>
<compilation debug="true" />
<!-- <authentication mode="Windows" /> -->
<customErrors mode="Off"/>
<globalization
fileEncoding="iso-8859-1"
requestEncoding="iso-8859-1"
responseEncoding="iso-8859-1"
culture="da-DK"
uiCulture="da-DK" />
</system.web>
</configuration>