title: Can't send mail from C# app
body: <p>I'm trying to send a mail from an app I'm developing but always get the same exception message: "Aditional Information: Mailbox unavailable. The server response was: 5.7.3 Requested action aborted; user not authenticated".</p>
  
  <p>Here's my code:</p>
  
  <pre><code>SmtpClient appClient = new SmtpClient("smtp-mail.outlook.com");
                  appClient.Port = 587;
                  appClient.DeliveryMethod = SmtpDeliveryMethod.Network;
                  appClient.UseDefaultCredentials = false;
                  System.Net.NetworkCredential Credentials = 
                      new System.Net.NetworkCredential(Properties.Settings.Default.systemMail, 
                          Properties.Settings.Default.systemMailPass);
                  appClient.EnableSsl = true;
                  appClient.Credentials = Credentials;
  
                  try
                  {
                      var mail = new MailMessage(Properties.Settings.Default.systemMail.Trim(), usrMail.Trim());
                      mail.Subject = "Usuario ha sido creado con éxito";
                      mail.Body = "Se ha creado el usuario " + usrCode + " en el servidor: " + Properties.Settings.Default.serverAdress + " instancia: " + Properties.Settings.Default.serverInstance + ".";
                      appClient.Send(mail);
                  }
                  catch (Exception ex)
                  {
                      Console.WriteLine(ex.Message);
                      throw ex;
                  }
  </code></pre>