I'm having problems with SMTP Authentication in C#
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I have an MVC 3 app and everything I try on my new hosting provider ends up throwing this exception:

**Server Error in '/' Application.
Mailbox unavailable. The server response was: Authentication is required for relay** 

I tried using the code from

http://stackoverflow.com/questions/298363/how-can-i-make-smtp-authenticated-in-c-sharp

which has many up votes, but I still get the exception.

My host has the typical panels that let me create mail accounts. I'm not sure about creating NetworkCredentials, what do I use as the User Name and password? What I've been using is the email address and the password for the email account.

Here's my code: 

    public static void sendMail(Joiner request) {
      SmtpClient smtpClient = new SmtpClient();
      NetworkCredential basicCredential =
          new NetworkCredential("garbage@stopthedumpcoalition.org", "ZS4rbO*7");
      MailMessage message = new MailMessage();
      MailAddress fromAddress = new MailAddress("garbage@stopthedumpcoalition.org");

      smtpClient.Host = "mail.stopthedumpcoalition.org";
      smtpClient.UseDefaultCredentials = false;
      smtpClient.Credentials = basicCredential;

      message.From = fromAddress;
      message.Subject = "Join the Coalition request from - " + request.FirstName + " " + request.LastName;
      //Set IsBodyHtml to true means you can send HTML email.
      message.IsBodyHtml = true;
      message.Body = "Name: " + request.FirstName + " " + request.LastName + "<br>"
            + "EMail: " + request.Email + "<br>"
            + "Wants to Volunteer: " + request.Volunteer.ToString() + "<br>"
            + "Organization: " + request.Organization + "<br>"
            + "Wants to become a Partner: " + request.Partner.ToString() + "<br>"
            + "Comments: " + request.Comments;
      message.To.Add("nivram509@gmail.com");

      smtpClient.Send(message);
    }



