Question

I am using the code as described in this question. However get following error when send an email.

Mailbox unavailable. The server response was: please authenticate to
use this mail server

Any ideas what could be wrong?

UPATE: Here is the code

System.Net.Mail.SmtpClient Client = new System.Net.Mail.SmtpClient(); 
MailMessage Message = new MailMessage("From", "To", "Subject", "Body"); 
Client.Send(Message); 

With following in App.config.

 <system.net> 
    <mailSettings> 
      <smtp from="[e-mail]"> 
        <network host="smtp.MyDomain1.com" port="111" userName="abc" password="helloPassword1" /> 
      </smtp> 
    </mailSettings> 
  </system.net> 

Answer 1

The code posted there should work. if it doesn’t, you might try setting the username and password in code-behind rather than reading them from the web.config.

Code sample from systemnetmail.com:

static void Authenticate()
{
   //create the mail message
   MailMessage mail = new MailMessage();

   //set the addresses
   mail.From = new MailAddress("[e-mail]");
   mail.To.Add("[e-mail]");

   //set the content
   mail.Subject = "This is an email";
   mail.Body = "this is the body content of the email.";

   //send the message
   SmtpClient smtp = new SmtpClient("127.0.0.1");

   //to authenticate we set the username and password properites on the SmtpClient
   smtp.Credentials = new NetworkCredential("username", "secret"); 
   smtp.Send(mail);

}