It looks like from your code you are specifying that the mail message's From field is based on the email address the user fills in. The mail server mail be rejecting this and only allowing email from the domain name example.com or perhaps the server name itself. I've run into this before where your From field must be the original site domain...
If you want to have the ability for the form-mail recipient to directly reply, use the ReplyTo field rather than the from:
MailMessage mailMessage = new MailMessage();
//try using a domain address that matches your server and/or site.
//the email address itself may also have to exist depending on the mail server.
mailMessage.From = new MailAddress("[email protected]");
//set the replyto field
mailMessage.ReplyTo = new MailAddress(txtEmailId.Text);
//send the mail...
Hope this might help...
EDIT:
After you've edited your question, the above is still relevant. It's very likely you cannot use a From address outside of your own site domain example.com. If you want to send two copies of the request (one to [email protected] and the other to the user as an acknowledgment), you simply need to add to the To property:
MailMessage mailMessage = new MailMessage();
//try using a domain address that matches your server and/or site.
//the email address itself may also have to exist depending on the mail server.
mailMessage.From = new MailAddress("[email protected]");
//add the contact email address to the To list
mailMessage.To.Add(new MailAddress("[email protected]"));
//add the user email address to the To list
mailMessage.To.Add(new MailAddress(txtEmailId.Text));
//set the replyto field
mailMessage.ReplyTo = new MailAddress(txtEmailId.Text);
//send the mail...
If you need to add a simple message for the user acknowledgment email you could also do:
try
{
MailMessage mailMessage = new MailMessage();
mailMessage.From = new MailAddress("[email protected]");
mailMessage.To.Add(new MailAddress("[email protected]"));
mailMessage.ReplyTo = new MailAddress(txtEmailId.Text);
mailMessage.Subject = txtSubject.Text;
mailMessage.Body = txtMessage.Text;
mailMessage.IsBodyHtml = false;
mailMessage.Priority = MailPriority.High;
SmtpClient sc = new SmtpClient("relay-hosting.secureserver.net");
//sc.Credentials = new System.Net.NetworkCredential("[email protected]", "MyPassword");
//send to only the [email protected] first
sc.Send(mailMessage);
mailMessage.To.Clear();
mailMessage.To.Add(new MailAddress(txtEmailId.Text));
//add a simple message to the user at the beginning of the body
mailMessage.Body = "Thank you for submitting your question. The following has been submitted to [email protected]: <br/><br/>" + mailMessage.Body;
//send the acknowledgment message to the user
sc.Send(mailMessage);
}
catch (Exception ex)
{
Label1.Text = "An Error has occured : "+ex.Message;
}